So my guess based on known results of the Denon AVRs and Marantz AVPs already tested, and logic, was correct, that HDAM adds distortions. Again, I don't believe the THD level as measured is audible. At between 0.01 and 0.05% THD, if one has the hearing of the normal 20 years old girl (I assume they hear better than boys) and in a very quiet room, it may be audible if playing tones, but for real world use I don't think so.
When I say "logic", I mean why would we expect it to measure better than the AV7705. It is already a nice surprise that it does measure slightly better than the AV7705 in some ways, and I actually find it hard to believe and can only guess the little difference could just be the statistical kind, I think, from the tolerances of certain parts, notably the volume control IC and the DAC to a lesser extent.