The material in magnets goes well into the 150-200C range before you have permanent losses depending on the mix
I don't know where RC motors come from, but I would guess its magnet composition isn't based on longevity or thermal property's, there is a huge range of materials and hence the characteristics of the finished cores
GM's Phd know way more than any of us will ever dream to know, and its proven they got it right with active thermal management of many aspects of the car.
My kind advice, quit finding reasons to get cold feet and just get the damn car ...
2012 Crystal Red Volt #10921 - Plug Powered #76