According to Brunning's books (Bruns interviewed DW in 1989) Dave said that he "heard from someone that was in the know that he was going to be replaced (in SB)". Still though, I agree with Macfan57 that it really was not very nice of FM to do that to Walker. Unless it comes out otherwise soon, I'll still believe that he left Savoy (at the height of their popularity too I might add) to join FM (as I recall Walker saying in the Brunning books that he thought/was led to believe that FM "wanted to get more rock and roll-ish at the time" (but of course was wrong about that).
I mean, if you were Walker, what else would you think if they were touring on the same bill and they invite you in? Naturally you're going to assume they want you to bring some input of what you do in to the ranks. I don't see why FM didn't even think of this as a possibility with him (or any of the other "shut out" Mac members, without opening more cans of worms).
I'm sure the Mac members wouldn't have liked it if that had been done to them. Even us, imagine if you were climing the executive ranks of a company but you heard that office politics were suggesting you might be transferred/laid off (nothing concrete mind you, but you needed a job to put food on the table obviously) so you left and joined another firm where some friends of yours got you in the door and they knew how you worked etc. Then you were told that the way you work needed to be changed (I don't know, say, they took you out of the office and put you in to an assembly line job at one of their plants, which physically you could do, but it just wasn't the work you were used to doing and it's not where your best skills were) and then a few short months later gave you your pink slip and said "oh sorry, it's just not working out how we thought it would with you so see ya later" and you watched your old job being taken and see your successors climb up above where you were in the organizational structure of your original employer on your way to the unemployment office. That'd kinda suck wouldn't it?
JMHO though.
John