And also, given that the stakes are higher e.g. in medicine, and the bar is lower in biology, one often gets a pass: "You don't want to poke anyone with needles, no LSD and no cages? Why are you asking us then?" Or something to that effect. The IRBs are just not used to such "harmless" things not being justified by the research objective.
Sometimes you might need to make the committee understand before a full review when you are asking where a line is for some tricky part, but you ask about those parts long before you have enough of the study designed to actually put it before the review.
Ethics are a personal responsibility. You should be personally embarrassed if you ever have something fail review, and probably should have your tenure removed as well since if your ethics are so bad as to put before the board something that fails you will also do something even worse without any review.
I submit unclear thing
Thing is approved
Thing must have been clear right?