I think it is a pure BIAB Bug (it has probably not been tested).

I think the user expectation is that the tracks are exported with the same name/title as the track title as shown in the Mixer or Track views and not with any hard coded default names for the tracks.

If I change the track title for each track with the Track Setting - Rename Track Title. Those names are used for the tracks within BIAB ie in the mixer and the track views. Those are the track names that I refer to in my production for the song and I would expect the same names/titles to be used when exporting a track.