Heat pumps are not resistive! That would defeat the whole purpose.
But the reduction of peak power is good. Not enough power between 5pm and 5:15pm because everyone turns their oven on, drop the voltage and everything takes longer, spreading the load into the next 15 minutes.
Bullshit. If the voltage is out of specs, the PSU should cut out. Very easy to implement.
Very bad design. A simple thermal cutout would suffice.
Except they do.