Meridian Ultradac behavior with Roon on Ethernet versus USB

I’m curious whether anyone has experience with this question. I have Roon core on a server (Innuos Zenith Mk3) and can output to the Meridian Ultradac on USB or ethernet. When connecting by USB, the Ultradac can be set up as decoder&renderer, or just renderer. The pathway shown in Roon reflects whether Roon is in pass-through mode (i.e. dac does decode&render) or decode mode, and the Ultradac shows “352kHz MQA” if it’s doing both decode and rendering (Roon in pass-through) and “352kHz PCM” if Roon does the decode, reflecting the format output to the dac.

Switching to ethernet, behavior is different. The audio settings for the Ultradac can still be switched between decode&render vs just render, but the behavior doesn’t appear to change. The pathway shown by Tidal is identical in both cases, and the Ultradac says “352kHz MQA” regardless of whether the configuration was pass-through versus Roon core decode.

So my question: does Roon default to pass-through for the Ultradac over ethernet, regardless of setting?
Second, does anyone have a reason to know whether there is any actual difference in the total processing, whether in hardware or DSP, when the DAC does rendering versus when it does both decode and render?

Can’t help -sorry - but wondering whether this has any bearing on @Matt_Farrar’s issue in this post?

Loss of sound quality and Bowers and Wilkins outputs disappeared

(based on an assumption that the Ultradac and 818 share the same interface)