It can be if you want it to. At Harvard, there's very few requirements on what courses constitute a degree, so if you want to get a degree by just taking the easiest classes possible, you can definitely do that. Of course, most students don't do that since that's not why they went there. I do think professors try to give higher grade averages for the harder classes to avoid punishing students for challenging themselves, but I don't really have a problem with that (if you chose those classes you're probably not in it for the grades anyway). Also, at least I'm the sciences, a good fraction of students start taking classes at the graduate level either freshman or sophomore year, since they'll have completed a good chunk of the undergrad curriculum in high school.

And then there's MIT.

I have heard the same thing about universities in Japan. High school in Japan is so much pressure that some students crack under it, but then once you get to university it is supposedly easily to just slack off for your entire degree program.