Throttled motor runs in PWM mode and it means that the current peaks are high. That means that IIR loses are higher than at contiguous current, plus more switching loses because PWM frequency is higher that commutation. Additionally those peaks must continue via diodes in switching transistors back to battery, and it makes extra IIR loses. And we fly all the time on motor, we never give chance ESC to breath like RC guys, so it definitely means we need ESC rated little higher.
Regarding security – I am not sure if ESC can switch off quickly after crash. I do not think so, I think transistor can explode earlier then ECS can react, but fortunately ESC can recognize locked motor as lost synchronization, and it is power (current) independent.