This comment made things more clear to me than the documentation that I saw, perhaps because I was looking at it from a Quest 3 perspective and their main page about it doesn't mention that at all.

I know what Open XR is all about but again, it's not clear which you should actually use for development if you're only targeting Quest devices, for instance. A little extra documentation would go a long way.

The same goes for all of the other things so frequently mentioned like their renderers.