That's right FredT, it's a preselected decelaration rate , always the same with or without reverse. That's the idea for the normal use of the auto brake system.
And that's right also, I prefer to stop 150 yards BEFORE the end of the rwy (even with a brake fire --> emergency evac) than 10 yards AFTER, in the mud and with a broken landing gear (well, the mud could be a good brake cooler, but....
Sabena ... Never to be forgotten (12 years already , what a shame !! )