OK. Thanks thats great, and makes perfect sense especially the comments about development history.
I've experimented with BIAB but havent saved anythihg yet just because I didnt want to clutter up with garbage. So I dragged solo tracks to RB prior to saving. Once I save it in BIAB, I see that I can open the whole thing in RB.
I have a number of other Qs - hopefully you good people with assist with those too - but will post those separately. Thanks all.