[apothegm]

The metal frame of a MacBook is part of the cooling apparatus. If something in the heat conduction chain got messed up (see the earlier comment about freezers and thermal paste), the chips are unable to shed their heat into the frame the way they’re meant to. Keeping the frame cooler than usual, while the chip quickly overheats.

[GWBullshit]

If the frame is ice cold, wouldn't the heat from the processor dissipate faster into any adjacent thing that is much colder?

[apothegm]

Air is a very poor heat conductor, and among the best insulators. The thermal paste conducts the heat much more quickly. If it’s not touching maximum surface area on the things you want to conduct heat between, and the heat has to dissipate solely through the air that’s touching the processor, that’s much less effective at cooling.