At this point, I don't think we'll get a proper answer as to why the adapters melt until we get something official from Nvidia or PCI-SIG.
As for the TBP of the 4090, it's indeed strange how Nvidia left those +50W extra there. Could it be for the transients? Like taking them into account so that a power supply that's able to deliver constant 450W of power will be able to withstand the surges without failing?
Please excuse my bad English.
Currently gaming on a PC with an i5-4670k@stock (for now), 16Gb RAM 1600 MHz and a GTX 1070
Steam / Live / NNID : jonxiquet Add me if you want, but I'm a single player gamer.