[nyrikki]

Same mechanism, different frequency.

Microwaves and radiant heat are both primarily EM radiation at different frequencies.

The frequency of microwaves was chosen due to the resonant frequency of water and thus is absorbed in the area near the surface of most food items, with radiant and kinetic heating spreading to the interior.

There is some minor differences with convection but a conventional stove heating element doesn't care if it is the air or the food that absorbs the photons it is releasing.

I guess the near surface of the food being directly heated vs nichrome wire producing infrared radiation can be considered 'very different'

But the need to preheat a conventional oven for even cooking is because it is mostly radiant heat transfer of infrared radiation.