“Insanely hot”, lets say go as fast as you can from 800 m to 600 m (the 200 m difference you describe) and stop at the end of this run as hard as you can:
the brake discs on all of my bikes get insanely hot then.
Vacation thing in the Alps, lets say 500 m difference, very fast run: the braking sound totally changes, ugly rubbing sound, surface of the discs will get quite dark and burned. But – up to now – this dark surface stuff will go away again when continue with normal trail biking. The brakes never failed.
“squeal”: only when mud and water is around. Pads rubbing on the burnt surface sound not like squealing… At least with my bikes.
And yes – the rear brake discs are the ones which turn quicker dark. Might be also due to the smaller disc diameter on the rear and more “constant” braking?
Used to run also sintered pads. But all my bikes have now organic low cost pads. Had more problems with the sintered ones (also peak force when braking is higher when using sintered).