Hey Tom.
This is fascinating, as I know for certain Apple’s DVDSP cannot work with 24-bit PCM files either - it will import them but they do not work properly (lockups etc) and Maestro is what DVDSP used to be until Apple ruined it.
I have no trouble at all with 5.5.5 WAV files in either Scenarist SD or DVD-Lab Pro or MEI DVD-A Creator, so it has to be something in the application - we do this sort of thing all the time too, and always, always use combinations of PCM & DTS - Dolby Digital has no place at all on music titles to my mind.
Would it be okay to send me a snippet of a file Maestro will not handle to recheck in Scenarist, DLP or MEI tools?
FWIW, using B-WAV is a very bad idea for DVD…or so I was taught.