One really must read the directions. As well as follow the instructions.
VFD's often greatly reduce the power required by a motor. They do this by incorporating a "soft start" control, as well as letting you run at a much lower level.
To use one example, a blower that was pulling 28 amps (single phase), was pulling only 8 amps (three phase), while the motors were both of the same horsepower rating. Why? because the blower was only moving the air needed- and not running full speed, fighting a damper.
As for lacking "heaters," well, the few VFD's I've installed all had equivalent circuitry in them. They also had protection for lost phases, etc- comparable to any 'electronic' starter.
I am NOT aware of the UL issue alluded to, and would appreciate some references. As I understand it, breakers (OCPD's) and overload deviced are intended to address very different issues. As the Brits would say, they are as different as cheese and chalk. I suppose "assembly" is the key word there.