I suspect they use a microprocessor to track startup currents on every install and then time-slice the currents to better control the current during each cycle of the 60 Hz coming in.
It does work when it hasn’t broken internally without notice.
Scary is I would never have known if I didn’t have weekly utility failures. I would have been dead in the heat during a hurricane. Can’t trust these people anymore.
I think the warranty on those things is only 2 or 3 years. Most of the ones I see are installed outdoors on the unit, so the components are exposed to weather extremes, even though the control box may be sealed pretty well. People have been using them on RVs for quite a while. I would think it would not be very difficult to replace.