You can load a Biab stereo render track into the Audio track of the BiabVST.
You can also generate up the tracks in the BiabVST then replace the tracks in the C:\bb\BBPlugin\SavedTracks\2021-02-08, 08-46-46(current folder) with the Biab generated tracks, keeping the same naming.
So copy the name of the BiabVST track, delete the track, replace with Biab track, rename Biab track to original BiabVST track name.

I don't know why bbw4_64.exe that the BiabVST uses can't open a frozen SGU giving the BiabVST the same tracks as the frozen song ?
If they modify the BiabVST to use direct from the source files then when you freeze tracks in Biab then open the SGU in BiabVST it will load the same tracks.