So WHY do I have to purchase a 6 pin to 6+2 pin dual pcie power cable splitter only to recombine the power inside of the GPU???
Wait, are you trying to power a graphics card that requires 2 connectors by splitting a single one?
While it's true that PCIE connectors can deliver far more than what they're specced for, I don't think going 100% over the spec is a good idea. There's a reason the card needs 2 connectors.
if he' just lack of extra 6-pin PCI-e out from powerful enough PSU[which is unlikely, cuz all reasonably-rated had two at least] its okay.
but when/if he's try to power card from splitted 6-pin-->2x6-pin or molex-->6-pin things from weak PSU, things can go bad very quick. with noise[explosive and somewhat dangerous. really]and smoke/burn and both PC owner and PC permanent dammage.