I know I'm stating the painfully obvious when I pose the question of why they didn't just include track-by-track credits. I would imagine it's probably just a space/design issue for the booklet. I'm curious if there was any flack for the TWGMTR credits being so odd (missing instruments, etc.), and if the more general credits are a reaction to that. Probably not.
Can someone just e-mail Joe Thomas and get track-by-track credits. It's fun but also weird that we have to do this process-of-elimination thing to decipher just a few of the credits.
For whatever reason, all the Thomas-associated BW projects have had odd credits. The Imagination ones are also missing instruments, songwriters, etc.
GIOMH also clumped all the musician credits together, probably to obscure the varying origins of the tracks. (Some were clearly cut in the mid-90s, one with Joe, the others in '03, etc.). Maybe it's a Mark London thing!
Some extra info, tho -- Brett Simons posted on FB that he played bass on the two Bennett co-written tracks, and that both were originally intended for the biopic. So it looks like, for awhile at least, that Brian was working on two separate recording projects.