I wager the electric motors actually have a very low angular velocity error on average. However given the way they work, during a revolution you likely have non

I wager the electric motors actually have a very low angular velocity error on average. However given the way they work, during a revolution you likely have non linear rotation of the shaft on a basic motor due to the classical physics of the rotational load accelerating between its push/pull magnetic poles. Theres some interesting work in the motor driver space trying to smooth out the curves in the motion profiles of the trusty stepper motor (see TMC2209 driver promo content) and surely similar work for other electric motors. I bet one of our peers here could speak more authoritatively than my conjecture above.