It seems that the Oculus app takes all running Unity Editor instances down when it shuts down for whatever reason.
This is an issue for development, as often we need to quit the Oculus app to use social features on Quest, which seems to currently lead to undefined behaviour (e.g. rich presence/destinations go all weird and crazy if someone is trying to use them from Quest while also logged into Oculus Home).
It would be great if closing the Oculus app wouldn't just go all berserk and kill any running Unity instances.
Note that this applies to both ones that are VR capabable (but not in play mode) and ones that don't even access VR at all, probably because Unity is "theoretically" VR capable.