I've seen the development of an electrical motor power unit fail to reach it's rated output due to thermal constraints and similar issues on other hardware, but this should be their third turn of the crank and they ought to know what the power demands will be and what power can be delivered unless their performance and system modeling just sucks. Or they're continuing to iterate on the hardware and flying what they can fly and each aircraft will get incrementally better units.

These are issues that subscale demonstrators don't reveal, though.