Spotify Connect Volume Control: Operating in Series?

Spotify Connect using the volspotconnect2 plugin seems to work with a ‘cascading’ volume control, where the volume control in Spotify operates on the sound volume level before or after the main Volumio volume control. That is, the volume remains quite low when either of the controls is very low and the other is high.

I am just wondering why this is so. Doesn’t this detract from the audio quality? I assume the audio from Spotify’s servers is the original bitstream and it should just be decoded and directly amplified, without a second volume control. Since I assume Volumio receives a chosen volume level from Spotify’s servers upon choosing volume via a Spotify client, shouldn’t that value just be synchronised to the Volumio volume control? I believe other devices with Spotify Connect work that way.

I have just updated to Volumio 3.378 and now experience the same thing you are reporting. Previously the volume control in Spotify when using Spotify Connect, exactly mirrored the volume setting in the Volumio web interface and either control would work seemlessly. Now having updated to the latest version, the two controls appear to be in series so that I cannot get full volume in Spotify unless I wack up the volume on the main interface. Very wierd.
Allo Boss 2 DAC on Pi 4
I have tried hardware and software volume control options. Grateful for any advice.