some more reading turned up this : POR-20 is heat-resistant to 1500 degrees F. I think this covers braking systems.
also to emphasize : as I am interested in rusty-metal paints, I am NOT interested in sandblasting. In that case, I would electroplate. I have already had this done to my brake calipers by a professional company. If rust is there, then it is there for a reason - i.e. technical difficulty in removal (by them, anyways).
and also to emphasize - I am not interested in brake caliper paints because I think brake fluid will strip it off, also there is curing to be done for true effectiveness - which POR-20 seems to avoid for some reason.
my Sebro brake rotors for my 1987 Porsche 944 NA have what looks to be primer gray on the “hats”. Got me thinking that e.g. POR-20 would be better for this application.