I don't think apple needs valve or steam's support to make their own VR gaming platform just as they didn't need their support to make iOS a larger app-store for games than steam is.
I think the more appropriate thing to consider is that Apple has a lot of Developers familiar with its platform
What's the figure when you compute the total engineering-hours into the games, though?
But, I think you're still on to something. The biggest strike against Apple in this space is the same strike they've always had: they've never seemed to take gaming truly seriously at a corporate level, by which I mostly mean courting (and spending money on) AAA-class developers. Maybe this will change, but they have a very long track record of snatching defeat from the jaws of victory in this area.
They had a partnership with Valve back in 2017 for Vive support on MacOS... Just three years later it was canceled. (There were actually more VR games running on Linux at that point than on MacOS, thanks to Proton.) I'm not expecting Apple to try to enter the VR gaming space again anytime soon.