I think non-contemporary college AUs can be really cool for sure, but... the whole thing is an AU. Putting characters in college is no less of an AU than putting them in a different decade.

Agreed. Do I generally prefer non-contemporary College AUs? Sure. But that's just a matter of personal preference/nostalgia. Does it require more of a suspension of disbelief to read a modern-day College AU? No, because an AU is an AU.