I obviously have as much of an idea of if/when these will hit Apple Music as everyone else here, but I've been a proponent of the theory that the Spatial Audio stuff Apple's doing is coming out in waves.
Launch had a scattering of albums, and mixes that definitely felt rushed to market
Then they started doing "featured artists", getting an artists backlog in Atmos at about a rate of 1 a month.
Then they launched the Spatialize Stereo and headtracking features in the most recent iOS updates.
Then Dolby Audio releases soft launch.
I can see them pushing this stuff more, and possibly announcing more formats (DTS, 360 RA, etc) the next time they announce new iPads, etc, which usually hits March/April. The Bowie albums so far are mostly later years albums, missing albums like Ziggy Stardust, etc. I can see Apple launching 360 RA support alongside a full finished mixed catalogue for the Featured Artist.
While Apple and Dolby seem to have a good partnership, Apple is clearly using their own binaural downmix solution for headphones/Airpods compared to the one by Dolby for PC and Xbox. You would only do that if the R&D was significantly cheaper than licensing (which considering Apple is heavily using the "Dolby Atmos" term in marketing, leads me to think that if they wanted it for dirt cheap, they probably could have gotten it), or if you intend to use it for other formats...