Avira, it is R Eliezer who mentions tiflus, not everyone agrees…
more importantly – how do we define capability? Definition of “gemora” is learning underlying reasons v. Mishna just halochos, not necessarily mastering tosfos. I am sure there are lots of ladies who are capable of learning and reasoning at that level at some topics. In my household, ladies are happy to discuss at that level agadot and issues that relate to interpersonal and practical application, with less interest in mahlokets Abaye and Rava.
Note that at Rambam times, women might have better emuna, etc, but they were way less educated both in Jewish and secular matters. So, if they are doing graduate work in secular subjects (legit, not gender studies), they need to understand Jewish subjects at the same level, otherwise, they’ll see it as tiflus.