Apparently the PCI-e bus is rated for up to 75W on the x16 bus, but the 1x link is rated for 25W.
I'm afraid that this point is unreliable.
I know this is documented in the pcie standard, but some gpu cards seemed to not obey the standard at all and would like to pull much more than 25W from pcie slots even if they are connected through 1x extenders.
Well obviously! Being a full sized graphics card is it allowed a full 75W of draw from the PCI-e bus. I would rather pull a full 75W of 12V through a 1x powered riser cable than my 1x pcie motherboard slots though, any day of the week. I can replace those if they burn out, and the mobo would be fine.
Regardless, I don't see how what you said makes any of what I said less valid. Using the EVGA thing to run more than 25W through PCIe x1 is over pcie spec. Will it burn up? Maybe, maybe not.