tbf I don't really like facebook, my wife is on it and it seems to be an utter cesspit of gossip and other rubbish.
However when it comes to VR I believe fb have a vision of building a community. Think big community big development and some very long term VR and AR vision. They can use their existing infrastructure to leverage user management and that makes sense.
Outside of AH you have games which are natively multiplayer and include always on voice comms. You have games like Onward where you join servers, are placed into a team, and can be playing with people from all of the world. This seems to be a common theme whether it is a FPS shooter, battle royal, strategy or sports game. I suspect FBs community vision is mixed in with a desire to dominate VR, but hey a decent managed community might not be that bad. I mean would AH be better if we had to use real names, and there was a big ban stick around the corner if you misbehaved?