Actually it is, if it is a good shooter right and left hand the impacts will be the same and if the shooter is still hitting low left then you could reasonably deduce that sights are indeed off. If the shooter is bad then instantly it will prove the point that it is the shooter that is the problem....not the gun. Since miraculously the bad shooter was hitting in one area then now shooting with a “unfamiliar“ hand the impacts move. Now if you read the the OP’s target his impacts are in the same area which means he is at least consistent with the error. The second observation is that the target distance was so close you don't even need sights to hit the target. At a few feet he would need the sights comically adjusted to make up for that bias. Now before you say I am wrong, remember that I have changed and adjusted the sights on Springfield polymer pistols more than anyone outside of SA. I have this same conversation with customers multiple times a day. Proving to a customer and getting them to admit that they are the reason they are shooting bad is just as important as adjusting sights Hence shoot it left handed see that the impacts move. Then lets try to adjust the shooter to correct the trigger pull With the dominant hand.Unless a person is 100% ambidextrous shooting with the non-dominant hand is always totally different so it's really not a logical way to say just swich hands to compare how a pistol itself is shooting. We all know how different we shoot with the opposite hand.
The issue is the user is handling a different pistol and therefore getting different results than what he/she is usd to with another pistol. The user must adapt to the new pistol.
My .02