The studies tell us that women with a high body count cheat way more than those with a low body count.

This is kind of tautological, though. The group of people with low n-count includes a lot of people (men and women) who have not cheated... because their n-count is 0 or 1 and you can’t cheat sexually and still have a 0 or 1 count. that doesn’t mean the 0 or 1 count people in the study will never ever ever cheat, just that their number at the time of the study precludes cheating. Thr high n group contains a higher fraction of the past cheaters for the same reason the n>2 group contains all the past cheaters.

And in your analogy, it’s fine to avoid purple grapes if you want, but you still have no idea which of the green grapes will become rotten. Every single purple grape in the high-n group started life in the 0-n green grape group.