I have never once had an exam graded on a curve. But I've never done any post grad studies, although from what my PhD holding mom says, it's more of less just a pass/fail system.

I've never seen or heard of that being a case.

The closest is test scores for admissions where the score is irrelevant and only the top X get in. But that's made apparent at the outset, whereas a curve is done after the fact if people do poorly.