You won't hear a trumpet suitably emulated by motors either. But that wasn't the question.
Any motor-based oscillator can be accurately emulated by a digital oscillator, so the answer to the original question is "nothing." But yeah, neither is good enough to emulate a trumpet played by a human.
The trumpet on my prophesy ain't half bad but yes I concede that point.
For synthetic sounds however, at this point I think it's mostly a question of workflow. Like yes you can take time to program all those imperfections into a digital sound. Or you can take time to make an analog device which has them inherently.
Indeed, motors are physical devices with their own imperfections. But … these are brushless motors, tightly controlled with a feedback loop. They, as they also say in their videos, very quickly follow input changes. I wonder how much weird effects you might hear on those.
