I suspect that if physics and/or CS students were required to take part in at least one study per class per semester (like psychology students - this may have changed since I last took a psych course), then I suspect that the results of university psychology studies would have greater representation.

Technically, people participating in those studies are supposed to be volunteers. Although if part of your "class participation" grade is a result of "doing" a study, then it might not be totally voluntary. And if those studies are unpleasant enough, then you really don't want to be a senior or graduate psych student actually trying to run those experiments.

We may never know, but I would think the results wouldn't be the same.

Mostly because there still is inherent bias against certain genders regarding a degree or a profession, e.g. men as nurses, women as programmers, and those would be way more pronounced back in the 90s.