That's the problem though. If many supposedly Atmos mixes are just going to be heard folded down to 5.1 or 7.1, that's honestly and truly going to follow that discrete intentional 5.1 or 7.1 mixes will better them. Now where the hell are we?
It really does work that way too. Folding down is a compromise. It may be small. It may be very well done. The ambisonic-like scaling in these 3D systems may be a legitimately clever idea and done well. But at the end of the day, there's either the original mix or a compromised version of it. In the same way that a 5.1 mix folded down to stereo can be lesser than an intentional stereo mix due to the artifacts that sometimes generates (yes, there are exceptions), there's going to be a divide between a full discrete 3D mix and a folded down render of it.
Two things. One is that most Atmos music titles on disc come on Blu-ray and it often (almost always) comes with a dedicated 2-channel mix and often a separate dedicated 5.1 or 7.1 mix as well. So it doesn't have to use a downmix in that sense (streaming would depend on what they want to offer).
Two is that at least on my Carver ribbon speakers with Sonic Holography, the 2.0 downmix of the Atmos version of Yello's
Point album is vastly superior sounding to Boris' own 2.0 channel mix (that is an option as well on the sane disc).
This is because all the sweet changes that were made to the album (like even deeper/louder bass hits or having centered vocals on Big Boys Blues) are still present in the downmix and the heck if my Carvers don't try their best to imitate the surround effects found in that version with sonic holography. Things that were in the surround speakers appear IN FRONT OF the Carver speakers almost to the listening location!
I had NEVER heard anything image directly in front of those speakers before in over 20 years with them! I was gob smacked! Yes, things would image off to the sides with many albums even wrapping around to practically 90 degrees to my sides with the help of Carver's Sonic Holography, but never directly in front of me yet in front of the speakers (rather than behind them).
But things often image in that location using front wides with my full 17.1 (11.1.6) home theater system downstairs. But this was a derived 2.0 mix! The official 2.0 track doesn't do anything like that on the same system so as far as I'm concerned, the Atmos derived 2.0 downmix is vastly superior in this case. Still, it's nice to be able to choose.
Steven Wilson's The Future Bites has a separate 5.1 mix from the Atmos mix. Once level matched, I'm not sure it's "better" or even that different sounding than the Atmos 5.1 downmix.
Of course, Yello's Point album sounds awesome (mind bogglingly so) in Atmos 11.1.6, but I have to say the 5.1 and 7.1 downmixes sound pretty darn awesome too. You just end up with the overhead stuff at ear level instead, but it's in the same x,y locations. It sounds awesome in 4.0 too (Carver ribbons + Klipsch surrounds).
It's all win win here, IMO.