If I remember correctly, the ESC provides a PWM output. PWM will cause more heating in the core than a 'pure' DC supply as the full voltage is applied even at small throttle openings. Coreless motors have the windings resin bonded onto the motor shaft than being wound onto a steel/iron armature and they are more susceptable to heating as there is less mass in the armature to absorb the heat. It is possible to use PWM controllers with coreless motors, but I would advise caution as it is not unknown to melt the windings right off of the motor shaft. On the other hand, I would have thought Kato designed the loco to be fitted with DCC decoders which use the same PWM technology, so I'm guessing they might know what they're doing
If at first you don't succeed, use a bigger hammer.
The only thing that keeps me sane, is the friendship I share with my collection of singing potatoes....
Never knowingly sensible!