Don't you need that already anyway? There's no standard for how universities format their academic email addresses.
Plus, .edu only applies to American universities. Services validating if you're a "real" student by checking for .edu emails were quite annoying during my time as a student. A lot of these platforms don't seem to even know .edu is an American thing.
Considering that many universities provide email addresses to alumni, I don't think that heuristic would work either.
I wonder what the benefit is.
I'm not sure how common it is, but my wife has an edu email address despite being well over twenty years from graduation.
Someone then asked what happens when we graduate and lose access to those emails, and they didn't have a particularly good answer.
I think that was also the same onboarding where they passed around a piece of paper for us to sign in with our name and social security number.