The BiabVST is playing the wav files back direct from the savedtracks folder and it's not currently using the dllelastiquePro3.dll to adjust the playback rate to follow a tempo map other than simple tempo changes set in the chord sheet that are pre-rendered in the wav.
It should be working like this within the BiabVST hopefully one of these days, where it is playing the source material direct from the realtracks folders and adjusting the playback rate and pitch changes as reaper is doing, so you will get instantly generated tracks with no waiting for rendering and any section of that track you don't like can be regenerated instantly.
This is a video demo for fitting a soloist to your tempo mapped live recording session with varying decimal tempos