Interesting. I don't know the answer but remember some Onkyo models have been mentioned in the aforementioned avsforum thread which is the most comprehensive exploration of this I've seen in terms of how any given AVR handles dolby dialnorm. Perhaps the default setting is off for that one and possibly the other Denon? This kind of testing is exactly what is documented in that avsforum thread but including many models.
I have to say I'd kill for one of those models that had zero change in volume.
It's becoming clear to me now how someone waving their hands about this might be looked at as a bit daft. If one didn't have the problem one might simply shrug their shoulders and think 'not sure what's up with that poor bastard's system'.
I can tell you if you *do* have the problem and have *any* kind of ear, it will drive you straight out of your mind, or at least to Apple Music and simply be done with it.