A single threesome is enough to put all its participants into those 20 per cent, and according to studies, 10 per cent of women and 18 per cent of men had a threesome.
There is a majority of the cohort already, and if your friends perceive you as judgmental, they won't likely tell you that they have had one.
There's no way 18% of straight men had a threesome. That sounds like the kind of thing people would lie about. In any case, a single threesome is not "polyamory" and certainly not closely related to "parallel dating."
There is a majority of the cohort already, and if your friends perceive you as judgmental, they won't likely tell you that they have had one.