Well, Dolby just wants everyone to set their Surround Mode to "Dolby Surround" (DSU) and leave it there FOREVER.
Now if the sound is already Atmos or DTSX, then that's easy. Just set the surround mode to STRAIGHT.
But I think the big question is, if the sound is in DTS or DTS-HD MA 5.1/7.1, should we use DTSNX (DTS Neural-X) or DSU (Dolby Surround) surround mode?
And if the sound is in DD or TrueHD 5.1/7.1, should we use DSU or DTSNXU ?
With the Dolby restriction, if the sound is in DD or TrueHD or Atmos, we have to use DSU and cannot use DTSNXU.