As far as we know, these are not simple upmixes. Dolby contracted a bunch of engineers and had them mix a couple thousand tracks in Atmos, which explains the scattershot approach to the back catalog (5 Queen songs, misc Motown, a couple Doors songs, just Rocketman from Elton John, and so on and so forth). Tidal actually lets you check on the mixing engineer on a lot of tracks if you're curious.
The Atmos tracks on Tidal are way too quiet, which has been a problem since the beginning, but that is a Tidal problem, not an Atmos problem.
The Future Bits and Abbey Road tracks on Apple Music are the same mixes as the Blu-rays, just at lower bitrates. This bothers some people a lot, others not so much. I echo everything Beerking said a couple posts up. In the long-term I think this is a good thing for the survival of surround formats and enjoy sampling a lot of surround music that I never would have tried before.