you are automatically assuming that noone can do FI just as good or better than nomod, so that's already a dumb point. It's all a matter of prefference, for example Tidek can do even better on FI than on nomod on some maps (he A'd blastix riotz with FI for example tho not pb)I can hardly believe that it increases his performance and he just doesn't want to use it.
It's probably only because he can't reach a high combo on that map (as you said it's "just" an A) so the shadow didn't go very low
I'm gonna ask him that personally to clear this up. Any other potential FI players you know of? I am always searching
But even if there are a few players who can play better with FI and they just don't want to, the amount is still way smaller than FL players so the point persists.