OK, but would you expect a 50/50 split if it was? And if you do not expect it, then how would you explain any remaining disparity?
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.
But actually, the question is quite easy to answer for me. I am more interested in sexism per se than in the gender distribution. When women in the industry infrequently report that they are experiencing sexism, then I’ll consider that we’re well on the way to solving the problem. The current gender imbalance is a symptom of the problem, not the problem itself.
This is the fox guarding the henhouse. There is no incentive for women to ever stop crying "sexism!" if this is the criterion in use.