Sounds like you've been using BiaB for a while.
I have been around since the floppy days also, but I don't stay in BiaB long enough to worry about FX .. when I use it I just use it to quickly find a style I want for a song.
Then, like you it's off to RB to get the real work done ...
However I *think* there is a way to add reverb to the overall mix (whole song) in BiaB, and maybe this aspect is what he is missing. I think I remember this being an option from reading release notes and during beta testing a while back.
Like I said, I don't use it enough to know where to find this setting in BiaB at this point, but I think it does exist and could be a possible cause for the difference.
I see some users explained it -https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=535763&nt=1&page=2
As far as FX on RT's, I'm pretty sure there are FX inside the source tracks on at least some of them, depending on the style.
I'm pretty sure there is a reverb on Piano Acoustic Rythm AlbertiMoody for example.
Never found it to be an issue, but pretty sure at least minimal FX are used to make the tracks fit together and sound as intended.
It may be done before the track ever gets to the PGMusic wizards (from the original recording artist/location) or it may be added to make the styles work.
I dunno, that's for PGMusic to clarify.