The positioning is definitely there with current Apple implementation in tvOS 12. Because the source is DD+ and not TrueHD, the decoded PCM signal is not of equal audio quality.Totally wrong. PCM audio doesn’t have the correct positioning as it was intended on a True ATMOS setup.
I was surprised myself to learn, that actually one can transmit Atmos also over a decoded PCM signal.
That is true, that no tvOS app (including tvOS itself) is currently able to send a verbatim bitstream out to HDMI.