> The rest of the STEM fields --- including mathematics --- have closer to 50/50

Citation needed for this. From a quick look from a paper: https://arxiv.org/pdf/1606.06196.pdf it seems like this statement is true at the undergraduate major level, but certainly not true at the doctoral level.

This is particularly relevant as unlike engineering/tech, where a Bachelor's (or less) suffices for the majority of work, the same is certainly not true in mathematics.

As an illustration of this, note that for many people graduate school in mathematics is spent trying to come up to speed with the current research efforts of the community, unlike engineering where one is (generally) expected to be a "producer" once one hits graduate school.