If I change the ZAxisMapping line to Option "ZAxisMapping" "4 5"
then scrolling works, and the other buttons become button-6 and 7. So I think it's quite likely that previously the ZAxisMapping line (the one mapping to "6 7") was being misread, and in fact the wheel was always being mapped to "4 5". That still leaves the vanishing sawfish bindings as a mystery, but they're dynamic, so it's not impossible to imagine them going, and it's of no particular consequence anyway.