[potato3732842]

We're talking about a niche professional organization with annual membership in the mid to high hundreds at the time. Based on what wikipedia says about the process of getting in I assume churn is stupid low. I would find it unlikely but not at all unbelievable that the rule was never actually tested from the mid 1970s until 1991.

Considering the subject matter of the organization it wouldn't surprise me if there were some other women pretending to be men who weren't kicked out. With really turnover being only 18mo in probably made her a boat rocking newb in the eyes of leadership at the time.