If this is true- what does it mean for Apple TV?

[priitv8]

... but the peer-to-peer doesn't support 4K/2160P, HDR (neither HDR10/HDR10+ or Dolby Vision) or Dolby Digital Plus or Dolby Atmos.

Where does this information come from?
I would dare to say the opposite.
As far as I can tell, UHD, HDR10, DD+ (with Atmos) all work.
Again, I mostly use Home Sharing (pull), but I don't see why it would not work over AirPlay (push).
I assume the underlying network transport protocol is exactly the same.

Dolby Vision profile 5 does not - iTunes ingests the file nicely but it will not be listed on tvOS side, so you can not play. Pushing it from iTunes itself (AirPlay) does not produce picture either, if memory serves me. I will re-test and let you know.

UPDATE: macOS does not support dvhe codec, so despite being ingested, there is no way to watch the Dolby Video clip in iTunes either. Neither do VLC or IINA support it.
Same story with iOS - Videos app does play only sound, screen remains black.
It gets a bit more interesting when trying to AirPlay. I tried both methods: from iTunes on macOS and from Videos app on iOS. In both cases, the TV switches to Dolby Vision mode, but the screen remains black.
Atmos sound plays as expected.

The bottom line - AirPlay supports UHD, HDR10 and Dolby Digital+ Atmos. Only Dolby Vision is not supported.