Hi Tom. If you have installed the audiophile version correctly over your old version, BIAB is unquestionably using the .WAV files. If nothing else, they load a bit faster. BIAB first looks for .WAV files and only when they are not found does it load and uncompress a compressed file.

What you are hearing is likely from another reason. For example, are you at a tempo considerably different from the recommended tempo for that RealTrack?

Did you try turning off Fast Generation for that song in Options, RealTracks?

Do you have a Mac or PC? What are the specs? Or, perhaps easier, is your single-core Geekbench score over around 1500?

It is true, those are two out of the three sounds most likely to show artifacts of stretching pitch or tempo (along with sustained acoustic piano). If you lower or raise the key by a half or whole step, do you still hear anything wrong?
BIAB 2021 Win Audiophile & 2020 Mac UltraPak. Software: Studio One 5 Pro, Adobe Audition CC, Notion 6; Win 10 64 Pro. Hardware: custom i7 16 Gb; Roland Integra-7, Presonus Studio 192, Presonus Faderport 8, Royer 121, Adam sub & monitors