I can't reproduce it following your steps but I have had this very (or similar) problem with ghost piano parts playing, not just this version but also 2022 and possibly 2021 (can't remember when the first time I had it happen but definitely pre-2023).

Unfortunately I can't remember exactly what the problem was but it took me a lot of messing about.

It was somewhere buried in midi channels or something, just another one of those oddities in BIAB where nothing makes sense or stays consistent. The track settings window, the various right-click menus all around midi channels or routing or something like that, which are supposed to affect the same parameters, but didn't correlate and wouldn't stick to what they were set at. Nothing to do with PGM or anything else you'd find in the list editor.

Creating a new song didn't get rid of it, closing and reopening wouldn't reset it but loading random styles sometimes did. I wish I could remember but sorry. Just endless trial and error solved it in the end.