FREQUENCY
Most "miracle" power deciders, rely on 60hz. What happens to the "miracle" (never mind the gizmo), should it ever see say 45 hertz loaded as the generator spins-down due to a fault? I remember seeing my first "Todd Industries" 75 amp switched high frequency charger. My neighbor called me over one morning.
"I wanna show you a 75 amp charger than is one tenth the size of that 200+ amp monster you have under your dining room table"
"Tah-Dah!"
Cough-gag-sputter went his genset. Turned out to be a clogged fuel filter.
"Say, can you come back over and give me a hand figuring out why the new charger won't charge. I got the generator running again OK, but no charge".
SMOKED
When you connect ANYTHING AT ALL to a standard generator, figure out if the load is frequency sensitive somehow. Some regulators now have cornering frequencies lower than 55 Hz. and a generator can fault and spin down leaving voltage available but frequency very low. I do not now if the miracle power gizmos were designed with this in mind. You should be able to get a straight answer from the gizmo manufacturer.