yes i think it does make sense. 'regenerate' means 'start again'. why did you regenerate?

when BIAB or RB creates a RealTrack instrumental part, the virtual musician plays around the chord sequence from a set of prerecorded phrases and licks. it can be different every time you regenerate.

RB allows you to regenerate the entire track to get a different 'take' or just a short section if you like most of the track but not a particular section or riff. indeed, multiriff gives you seven different choices.

by regenerating all or bits of a track you get a finished instrumental part you are happy with(using cut and paste from several different 'takes' if necessary).

when you have the tracks you like for every part, then is the time to mix it with volume changes.

if you mix then regenerate it's like saying to a live band 'ive done the mix but now can you play it again?'. the band might play something different that doesn't work with the volume changes you recorded.

so yes i think what happened to you does make sense.