I don't care how Reaper works. I have no interest in Reaper. (as I mentioned earlier)

BIAB randomizes generations - bits of recorded takes unless frozen. Sometimes you get decent results per X bars, sometimes you have to assemble from different parts. What to not understand here? In your version of "arranger" you show opened audio files marked/mapped for individual arranger part. Who decided that those are the best choices for that specific arranger part? You - dear musocity! Grooves can change significantly musically if proper partial or whole generations are applied. Are you the ultimate decider on what would work best for arranger Part A, Part B, etc?