Testing at cable manufacturer Linwell, by YouTube channel Hardware Busters, shows in excess of 600 watts coursing through the new connector for 15 minutes and only hitting 46°C at both ends of the cable. But here's the really impressive bit. That applies both with the cable fully seated and barely in contact.
In other words, you can have the new 12V-2x6 only partially inserted and it won't overheat. At least, it didn't in this test, again with over 600 watts of power, which is a fair old lump of electricity.
Of course, this is just one test. With the old 12VHPWR connector overheating wasn't a nailed on certainty, even if the connector wasn't fully inserted. Yes, it certainly did fall over on occasion, sometimes melting both plug and socket, but it wasn't something you could be confident you could force to happen.
It's also worth noting that this latest testing actually bypasses the new connector's safety feature designed to prevent operation when not fully inserted. The 12V-2x6 connector's sense pins, which are designed to detect when the connector is pushed fully home, are further recessed into the casing.
In normal operation, the connector will not function if the sense pins aren't seated. This testing bypassed that feature to demonstrate that even when not fully seated, the new connector is safe.
Anyway, while this is perhaps not the final word on the ability of the 12V-2x6 connector to avoid overheating and melting, it's certainly a good early indication that the new design functions as intended.
And having a GPU that you are reasonably confident isn't going to melt is extremely welcome. As we've reportedly previously, the new connector is already being fitted to new graphics cards. So, hopefully the whole 12VHPWR fiasco will soon be but a distant, smouldering memory.