Its one of a number of failure points, the killing of the GPU isn't tied to one specific failure. Various ICs on the GPU were shown to be impacted.If solder on the graphic card is melting I’d assume this is heat issue,
As for the solder, I think its more along the lines of too much power traveling through a weakened joint that caused it to fail. So to my uneducated perspective, I don't think the heat was melting the solder away but excessive power was travelling through the circuits causing the circuits to burn out (yes I'm using a word related to heat). I'm trying to make a distinction where the GPU gets hot and the heat syncs unable to cool the GPU vs sending over 400+ watts onto circuits/components not designed to handle such a load