Getting back to the session musician thing: ya know, some of the guys who were in some of the more famous Anglo bands also did some weird sessions. Steve Howe I guess must have gotten friendly with Trevor Horn, because Steve guested on the first Frankie Goes To Hollywood album and at least one other Horn related project (I forget what it was, but he said he played his fretless Fender Jazzmaster, and "There may actually be some of it present in that quagmire of a mix", which suggests to me that Steve himself is doubtful that his contribution actually made it into the final mix).

And I think Bruford might regard things like ABWH and the Union album and tour (and possibly his presence in 80's/90's King Crimson to be) "the day job", i.e. something he did to get a big paycheck so he could go off and do what he wanted to do on his solo records. I think he said there was a tradition of that in jazz, so he considered it an acceptable way to go about things.