I'm not active at all on Facebook itself - checking now, my last post was >18 months ago, and and other interactions (likes, comments, etc) even longer. But I leverage Messenger for a few contacts that prefer it, and that Messenger use seems to be sufficient to ward off the inactivity trigger.
I'm surprised they don't just treat the Oculus usage similarly, and count that usage as "activity" in the context of considering an account active/inactive.