Probably not. If you ride two versions of the same board, one with a slight setback and the other without, back-to-back in a powder situation... yes, the pickier riders will notice.
If you're a rider like BurtonAvenger, I'm sure you can discern the difference on any condition.
What I can personally tell you is this: if you give me a directional twin board that has had the stance centered to be twinned out, I will be able to tell. Setting yourself in front of the sidecut alters the performance noticeably even if it is half an inch because you are now in front of the narrowest part of the board. Your regular riding will feel like your switch.