Slide-to-frame fit is one way of ensuring that the lockup is consistent at each cycling of the action. Too much slop equals too much variability in the alignment and lockup of the barrel to the slide (particularly the locking lugs recesses). Some people make a big deal out of it, and it is important, but it is not the determining factor in accuracy.
Never try to educate someone who resists knowledge at all costs.
But what do I know?