Yep - If you were to look at this other part of the wiring diagram, the input from the Stop lamp comes from a NO switch - which makes sence, so those other ones are NC, so I think your right Ben.
So with no 12v on those inputs, it looks like Im driving around with the brake on, and if that isn't tuned out of the tune then that might be an issue. Its an easy fix to add that in regardless, and certainly wont hurt things.
this is the stock commodore brake switch with multiple outputs as well, so Im assuming 2 are inverted.
cheers