As far as I know, in the Castle Creation Phoenix line, the ESC uses the pulse length from the timer/throttle to set an appropriate count rate---the ESC counts the magnets as they rotate by the armature. That is why the kV of the motor doesn't matter. As long as they have the same number of magnets, any motor will give the same rpm if hooked to the same controller--within the limits of the voltage available of course. A motor with a different # of magnets will just scale its rpm. Common magnet counts are 10 (the Brodak stock motor and high kV type motors), 12 ("CD ROM" type motors), and 14 (most AXI and Scorpion "standard" motors). Of course I am talking about outrunner brushless motors. Inrunners have a lot fewer magnet poles (2 in one I have).
"Clearly" there is no issue in the counting (because it has to have that circuitry to know when to do the electronic commutation for the brushless motor), but in order to get a rate (=counts/unit time) it does need a clock. Also that clock is used to convert the timer/controller pulse width into a digital value (or equivalent) to make the pulse rate comparison. So my guess is that this clock might be sensitive to temperature changes.