In the player tab, I unselected "enable server", which revealed the Music Clients menu and there was upmpdcli selected as a client. Presumably, I had selected it days ago during a previous test and when I switched to MPDv20 as server (which makes the client menu disappear), I assumed this would disable any clients but that might not be the case.
So I unchecked both enable server and enable client...save, then enabled only MPDv20 and went back to the snakeoil menu. Sure enough upmpdcli was no longer greyed out.
I didn't bother uninstalling it. To my ears, the previously great SQ of MPD alone was already restored.
I wonder if this is an example of what @"hkphantomgtr" said "Added upmdcli, even I don't use it, it already deteriorates the sound."
...or AK might tell me upmpdcli was never actually running, in which case I may have imagined it.
