I will fire up my P4P and check, but I am pretty sure it is associated with OA only braking, with OA off I don't get that message even when the AC is braking due to letting off the sticks.
Randp4p, I just got done testing this pretty thoroughly in every mode I can think of, I only get the "Braking now" message when OA is turned on and the AC is braking due to a detected obstacle. Even when I tried flying hard and letting go of the stick, when the very hard braking is deployed by the AC, I don't get any message about braking at all.
Yeah, that's Skipper and Digger, Golden Retrievers, soaked from swimming in the river and asking if they can come in the house dripping wet, so out in the yard they stayed... begging to come in. Hard to go wrong with Goldens!