^ This is a great discussion point, and I'll venture my viewpoint.
The problem isn't the tool.
If we could shoot real firearms at each other, then yes, that would be a great way to get used to the stress. But alas, our physiology is prohibitive of that intense of a training regimen.
And certainly, live-fire in a 360-degree training environment such as the shoot-house makes for amazing training in real-time problem-solving and decision-making within the context of the active gunfight, but its focus is restricted to techniques, tactics, and marksmanship - even with a remote-controlled robot target, only so much can be done.
Simunition as well as other substitutes such as UTM and RAP4/T4E and the like, along with "lesser" simulators like airsoft all induce a bit of stress via some level of pain, but it's really less about the stimulus than it is the value for which it gives the training. The pain isn't the real value: the value is the ability to simulate real-life decision-making, with another real-live person on the other end of the muzzle.
Our current understanding of how we as humans process information and perform tasks is that we aren't truly able to "multitask." Rather, that we are instead able to "stack" tasks simultaneously. The degree to which we can successfully stack tasks depends on just how much mental/physical resource we have: at some point, our ability to stack as based on those resources is overwhelmed by either the complexity or number of tasks. At that instant, while the mastered fundamentals remain, tasks for which we are
challenged to perform become the first points of failure. We can see such failures in both training and in real-life. I've cited my fellow students' shortcomings (i.e. when a fellow student literally froze-in-place after he verbally challenged the threat target, instead of flipping off the safety and engaging) as well as my own (
https://www.thearmorylife.com/forum/threads/red-dot-sight-assistance.521/page-2#post-9159 ,
https://www.thearmorylife.com/forum/threads/lets-see-your-ar-setups.258/page-2#post-3579, and
https://www.thearmorylife.com/forum/threads/what-kind-of-plate-carrier-rig-do-you-run.436/#post-7264) in the shoothouse. And in much the same way, I've cited incidents such as when ex-officer Potter mistook her service weapon for her TASER, as well as this unintentional discharge in Las Vegas -
Video: officer almost shoots partner and suspect . The lack of sufficient stress-inoculation means that we are overwhelmed that much sooner.
Much like why martial-artists spar or a new surgeon engages in his/her craft under the eyes of a watchful master, the idea is to gradually increase stress: to allow the individual to become hardened through the crucible - and this is essentially what Force-on-Force training is. It's about "pressure cooking" techniques and tactics in real-time, versus a "thinking" opponent (note here that the scenario often becomes the constraint of exactly what kind of interactions can be had - unscripted, open-ended combatives is extremely hard to incorporate into a coherent training regimen), with as-realistic of physical stimuli as can be provided, whether it's being shot with a Sim/UTM/rubber or paint projectile/BBs, being touched with a No-Lie Blade or Shocknife, or getting to pound on each other with High Gear suits.
The primary goal is that we stress-inoculate our decision-making processes so that should the time come, we are better able to "stack" more critical tasks.
You're absolutely right: airsoft is a poor substitute for the real thing where it comes to weapons manipulation. Simunition/UTM allow for much more realistic training in terms of weapons manipulation, as these tools not only typically function the same as their live-fire counterparts (oftentimes these tools are one and the same as their live-fire counterparts, only with critical components substituted so that they can only discharge training ammunition, not live cartridges), but their unique training cartridges/barrels/bolt-assemblies/magazines sometimes have the propensity to actually induce more stoppages than what's typically seen of their corresponding live-fire counterparts (Warrior Poet Society's free YouTube videos as well as their Network FoF content really demonstrates this very well) . Not only that, but as they are functionally nearly identical to their live-fire counterparts, heir stoppage-reduction/remediation methods are thus also identical to that of their live-fire counterparts. So, unless weapons manipulation is the actual point of the training -in which case the incorrect training tool was chosen- then it should be considered that there may well be other reasons for which those classes are held (it should also be remembered that there have been times in their lives that some now highly thought-of and sought-after individuals in the industry have taken side-gigs as gun-shop clerks in order to make ends meet: Varg Freeborn is among today's most well-known integrated-combative instructors, with seminars offered at some of today's most highly-regarded training symposia, but at one time, he was making ends meet with just such a side-gig, while he built-up his training business).
Similarly, you're also absolutely correct in that the 6 mm, 0.20 to .36 gram plastic airsoft BB (usually limited to < 1.5 Joules of muzzle-energy for safety) has limited effective range and sometimes horrible external ballistics. However, at typical "CQB" ranges (including typical engagement ranges for most "unknown contact" scenarios in real-life, even outdoors), quality airsoft replicas can deliver that BB just as accurately as either Sim/UTM conversions or the live-cartridge firearm. To-wit, IPSC Action Air is an internationally recognized competitive shooting sport (especially popular in those areas of the world where handguns and/or their licensing are either legally prohibited or ownership otherwise limiting), and uses the same basic principles as IPSC (here is a post from the early-oughts on the Brian Enos Forums -
https://forums.brianenos.com/topic/11690-reduced-scale-targets/ - and yes, you can probably guess who "DumboRAT" was, by the writing style
), only with target distances/sizes scaled to allow for airsoft engagement:
(Vitaly Kryuchin makes an appearance about a third of the way through this RedWolf Airsoft sponsored video)
Just as any of these training tools can be used in a less-than-ideal manner, so can airsoft. Force-on-Force itself can be turned into a game (due to inadequate scripting or simply bad organization - or improper participation by either the role-players or the student: of the latter, students can get "Train-itis," whereby their goal shifts to that of wanting to "win" the scenario, instead of proceeding through the scenario as they would have done in real-life, and maybe failing, but actually learning something from it
), and combatives training can be in-turn physically worthless (i.e. insufficient resistance/effort offered by training-partners or role-players) to dangerous (folks who interpret the training paradigm of "uncooperative and competitive" to be synonymous with going at it 10/10ths).
I've participated in some really great Force-on-Force. I've participated in some really bad: either due to improper equipment (I've yet to use Sim, but I've used all of the other tools that I'd listed in this thread....oh, and to be completely up-front, I've only played with UTM, I haven't actually yet participated in a class that used UTM), instruction, or role-players....or, yup, even problems caused by yours truly, who didn't know better at the time.
It's not the tool's fault.
Besides, we've all seen farces made of both flat-range (VODA comes to mind) as well as shoot-house (remember when 10th Mountain officially apologized?).