Generally I agree. The only potential difference between heat damage in a brushless and brushed is there are no halls to die in a brushed motor.
However, there is a curious thing that can happen to a brushed commutator when it's too hot and you push too much current thru it, especially at high RPM: A Plasma Fire.
You don't want that to happen.
I dont' know if it makes a difference temperature-wise, but many brushed motors still use ceramic magnets, instead of rare-earth, probably because of their size. So if the ceramic magnets can run hotter before demag, then so can the rest of the motor, but if they have a *lower* demag temp, well....
I know I used to run those little radiator fan motors on the original DayGloAvenger until they were hot enough on the outside case to instantly turn ice water into steam, and that's with the motors bolted to the large aluminum plate (4x rackmount faceplate) that was also bolted to the aluminum bike frame, with airflow from riding and from the rear tire/spokes cooling it.
I don't want to know what the armature temp was.
Yet, they still worked apparently just fine, and never even melted the plastic encasing the armature windings themselves (they were brushed 4-pole axial flux motors, coreless, with the windings flat-mounted and cast into black plastic disks).
Though, I think if I'd had a battery pack capable of *sustaining* those power levels for very long, they probably would have turned into slag inside.