I’m curious how this case would play out if some males applying to CalTech did this against female applicants. That said I’m not sure how much gender based affirmitive action there is in science/engineering today.
Potentially quite a bit. Here's some recent data about admissions into the highly-competitive Illinois CS program: https://www.reddit.com/r/UIUC/comments/12kwc4a/uiuc_cs_admis...
Note that admissions rates for female applicants are higher across all categories—international, out-of-state, and in-state. Obviously you can't fully tell what's going on here without more of an understanding of the strengths of the different pools, but a 10–30% spread (for in-state) suggests that gender is being directly considered.
IANAL, but I'm also concerned about the degree to which this decision affects the use of other factors during college admissions. Fundamentally admissions is a complex balance between prior performance and future potential, and only admitting based on prior performance means that we're stuck perpetuating existing societal inequities.
From the data you present I suspect that there is weight still given to gender. I wonder how much energy there would be to investigating this? I wonder how many guys who get rejected from MIT CS will now do Tik Toks about how a girl took his spot, since he can no longer say it was a black kid?
http://www.differencebetween.net/miscellaneous/legal-miscell...
This article [1] indicates that state schools cannot discriminate, but private schools can. It's a decade old, but I can't think of any intervening laws/cases that would have changed this analysis (IAAL).
1: https://fedsoc.org/commentary/publications/affirmative-actio...
It could be very well true that some or many institutions are violating the law, but I don't think that negates the point that I made about what the law is.