Digging more
On the Firecore Forum talking about Infuse streaming app for Apple TV is mentioned very clear that dolby truehd and Dts hma because of the very high quality will cause problems for Siri and therefore if Apple finds not a solution, Siri is first priority, we will never get lossless on a Mac or Apple TV
Thats a theory from 1 guy on that forum who explicitly said "...I could be wrong..." and just "read it somewhere" - probably on Reddit here. Reddit is full of confidently incorrect people.
Plus it's a weird theory since I think Siri in Apple TV is input only. I have never ran into an instance where Siri talked to me from the Apple TV. It will take commands from the remote, iPhone, HomePod etc. I do however have a HomePod, and the HomePod could be taking over the voice feedback. Plus, the Shield has Google Assistant built-in, and obviously no trouble with pass-through, and Google/Android TV software/hardware is hot garbage. I only have a Shield for lossless pass-through. Otherwise it's a buggy POS.
If Apple doesn't implement lossless Atmos pass-through, it's because they dont care about it since 99.9999% of their customer base doesnt care about it.
I'll be the glass-half-full guy, and say that I think awareness of lossless multi-channel audio is getting a bit of traction. Lossless multi-channel is not like the 2 channel lossless vs 320 kbps mp3 debate. In the case of multi-channel, the difference is astoundingly obvious to the laymen with either music or movies.