I thought it was the metal fan in front of the magnetron that scattered and randomized the microwaves so there aren’t any hotspots.

Inverter microwaves allow you to change the power level without duty cycling

There’s nothing a bit of inverting the polarity can’t fix!

Not directly, but they improve the low-power modes substantially, and using the low-power modes for longer times is the solution. Inverters aren’t strictly needed, but they do make it better.