I remember it being the case before too. It wasn't unconditional like it is now. For example, I distinctly remember being able to scroll through someone's profile in a normal browser window without being logged in, but in an incognito window, I was immediately told to log in or create an account.
They may have had other heuristics too that led to inconsistent behavior between users. So it should not be so surprising if some people report that that happened even though it didn't happen to others.
