I think so. When I signed up for Discord, it also automagically grabbed my Gravitar. Dunno how. Exact name match, maybe? Email address?
I think it's pretty great that all I have to do is enter my SL name when registering somewhere and my chosen avatar populates all by itself, that's the whole reason I got a Gravitar - although I have to log into Gravitar proper sometime and update it, it's a pretty old one by now.
BUT I do wish sites told you during registration in like a PROMINENT way that they sync with Gravitar, because signing up for new things under my SL name nowadays is rare enough that I forget about the whole Gravitar thing in between, so that when I register at a website and suddenly see my avatar appear all by itself it's all jarring and vaguely paranoia-inducing for a few moments until it occurs to me what's going on.