Er, lots apparently. Just now I was searching through posts on a Facebook event to find more details. I thought I finally found what I was looking for buried a few months deep and clicked it. It was the wrong item so I clicked back and Facebook scrolled me to the top of the event page again.

This is a common occurrence for me on Facebook on both mobile and desktop. It happens sometimes in Gmail too. I'm certain I could find a half dozen other examples given five minutes to go test.

Meanwhile HN happily preserves scroll position perfectly.