in a way this kinda ties in with what Steve Genewick intimated in that interview that got posted at QQ recently (can't find it at the mo.) where he was discussing the advantages of Atmos over 5.1 and he said (sorry, i'm paraphrasing like mad but to the effect of);yep. can get even weirder if you get fixated on trying to optimize across room/apple spatial/binaural.... one can go crazy
"5.1 flopped because it didn't work outside of the studio".
so, nowadays, i would sorta imagine an Engineer mixing in Atmos would be working to make things primarily sound at their very best in the studio in the original channel configuration (i'm guessing that would be 7.1.4?) but then (as we've seen many Engineers say over the years) they would take their mix and try it out in various other places/systems/configs (Elliot Scheiner for example not only mixed on Yamaha NS-10's to get that generic kinda Japanese consumer electronics sound but also liked "The Car" to get another perspective on his work) and so in a similar way now i suppose you've got to see how Atmos mixes work out on all sorts of playback equipment, including AirPod Pro's etc and its not enough to cater for one end-user/delivery configuration anymore?