Yes, it is safe to use a single 8-pin connector with dual 6+2 pins on an 8+6 pin card.
Yes, it is safe to use a single 8-pin connector with dual 6+2 pins on an 8+6 pin card.
It makes sense that the cable, especially the one that came with the PSU, should be able to manage the power output of its connectors. For example, if the PSU cable includes two 6+2 PCIe connectors each rated at 150W, it's likely capable of handling 300W. If it only has one 6+2 connector or a 6+2 with a 6-pin connector, I wouldn't anticipate it supporting that level of power.
The manufacturer's warning seems to be aimed at discouraging the use of low-quality third-party cables that could harm the PSU. As long as the alternative is a dependable and reputable brand, there should be no issues.
I understand, thank you for clarifying. It’s clear the manufacturer’s choice is logical. Unfortunately, the top-quality cables available online are either 6pin to 6pin models priced at €2.2 each or you have to order from AliExpress. No other shopping site provides reasonable shipping costs here, as the shipping fees consistently exceed the product value.