I spoke too soon. (I think I just anticipated it was solved without testing it more.)
BIAB does still load the WAV file if it exists (with same name).
The option is only for MP3/WMA as it says, so I guess there's no option for WAV - it just opens it automatically whether you like it or not.
So the 'solution' is to not have a WAV file with the same name in the song folder...


BIAB 2012.5 (upgraded from 2006), Windows 7 64-bit.
Guitarist and Worship Leader from Townsville, Australia