You are talking about a hypothetical scenario where all sexist stereotypes are eliminated. It’s obviously silly to guess at what the numbers would be. I see no reason to expect a precise 50/50 gender balance in every one of the listed fields. Conversely, I would also not expect to see the massive disparities that we see currently.

The problem in STEM isn’t that the gender balance isn’t exactly 50/50. It’s that substantial numbers of women are discouraged from STEM careers by sexism.