There is more than one version of this movie on blu-ray. Your particular disc has a DTS-HD MA 2.0 48/24 track. I can’t find any information about version of this movie having a DTS 96/24 track. New Denon models have up mixer restrictions for DTS/DTS-HD 96/24 2.0/5.1 tracks but that will not be an issue here.
“So, their AVRs NEVER show just "Dolby Surr" or "DTS Neural:X" by itself on the front. MY unit DOES show this on most content activating the upmixers, so I thought something was wrong.” Your unit should display “DTS Neural:X”when playing a DTS/DTS-HD 2.0 48/24 track because it defaults to the DTS up mixer. It should display “DTS/DTS-HD + Neural:X” when playing DTS/DTS-HD 5.1/7.1 48/24 tracks as that is the default for DTS multichannel tracks.
If the receiver is behaving in a way contrary to the way it should be behaving according to Denon’s manual, contact Denon for help. Before doing so, study the manual. You may find it is doing exactly what it is supposed to be doing regarding a given signal.