Ah, now you’ve gotten where I was in the 4th comment in this thread. 
This points to the DSD muting implementation of the DAC platform… And it does not answer the question regarding why my Audirvāna 3.2.2 DSD256 playback scenario is near flawless… (For reference I apply (.5s) of sample-rate change latency).
Until @Jason_Pasosky provides computer platform/OS information/Audirvāna configuration, we cannot correlate the behavior to a computer system and OS.
Perhaps the UPnP transmission buffering produces enough latency to obviate the transition noise in certain playback scenarios with certain DACs.
As Jussi says in your quote from him above, HQPlayer takes care of DACs that don’t properly implement DSD silence at beginning and end of playback by playing silence of its own. (HQP did not do this previously, but users complained so Jussi added it.) Audirvāna 2 did this (played its own DSD silence to provide for DACs that don’t), but for whatever reason Audirvāna 3 no longer has this ability.
And now you’re all caught up regarding why some DAC and software combinations have pops when starting and ending DSD playback, and others don’t.
Don’t flatter yourself… I have been pointing-out these potentials for quite awhile now in many posts… Just not specific to HQPlayer… All you know is in the context of your experience..
You are presuming that Audirvāna has changed the handling of DSD signals based on your experience with your DAC playback scenarios, which proves nothing… Especially in the light of my near flawless USB DSD256 playback on macOS + Audirvāna Studio 3.2.2 via my playback system architecture…
I don’t see a lot of users jumping into this thread… This tells me we are addressing a couple of corner-case USB playback scenarios here.
Audirvāna does not control the clock topology of the DAC platform in regard to DSD signal muting… The USB transmission is asynchronous, therefore, the DAC platform clock topology is managing the DSD signal mute timing. The DAC design is the functional controller of the signal behavior…
Because Roon or HQPlayer appears to compensate for the limitations of the DAC mute functional timing, does not necessarily point to some failure of Audirvāna to provide for compensation… because the Audirvāna audio-engine does provide compensation… and it is found in the DAC Input settings where latency can be added to sample-rate changes and muting between sample-rate changes above and beyond what might be inherent in the fundamental DSD playback engine architecture of Audirvāna.
It was stated by Laako, that HQPlayer does not add silence between tracks…
So, until you can pull-together a consensus regarding this behavior in some playback system context, the variables are salient in this contextual DSD256 playback scenario.
My experience is distinctly different than yours, and Jason_Pasosky … And this is contextually relevant.
Can you send us a copy of the "Debug Info“ when you have this issue? You can get it in Audirvana Settings>My account.
Note: When you click on the Debug Info button, Audirvana automatically copies all its content. Please paste it in response to this message.