So I am not an electrical engineer, nor do I work for Asus, so take everything I say with a grain of salt.
That said, we all know the 12V-2x6 cables are problematic, to say the least. And this after updating from the original 12VHPWR. You are putting too much power through too small wires on one hand (similar to how you can overload your home's electrical system if you try to draw too much power over lower gauge copper. For example, you can't power your oven or electric dryer over a regular 15-AMP circuit, even if you rewire it to be able to plug it in.) NVIDIA unfortunately exacerbated the problem by not allowing any sort of fault detection circuitry. So say you have a fault with either the connection (on either end) or the physical wires themselves, the rest of the wires will still try to draw the power it needs. Because there's a less than 10% overhead buffer, you can very easily overload the remaining wires and overheat/melt them, because they're trying to draw power that exceeds their specifications.
Now, this is not as much a problem for the 5080 or lower, because their power draw is a lot less than the 5090. So even if you have one or two faulty connections or wires, and the remaining wires are drawing the power, they likely will not exceed their specs (or at least at such a crazy rate to cause fires/melting issues). The 5090 on the other hand is very power hungry.
Because of the lack of circuitry to detect a fault PER wire (they saved room/expense by only having one circuit to determine if the card is powered for all the inputs), all the card knows is "Yup, I got power" and it keeps trying to draw. It doesn't know if all 4 (in the 5090's case) of the connectors are working properly, or if 1 or 2 or even 3 have failed, and it's trying to draw massive amounts off so few wires.
In either case, I would think the connectors that came with your card are safer. They are newer, so theoretically should not have wear and tear, and they look to be better insulated/manufactured. It's only 3 PCIE connectors for the '80, and at max load, you might run into a few issues if one of them is not working properly.
Thankfully, the Astral circuitry (only card currently being sold that I know does this) does have circuitry that at least tells you you're not getting the exact clean power you're supposed to get. It won't tell you the exact issue, other than "yo, something is wrong, turn me off please and get your connections checked out".
The 5090 is walking an even thinner tightrope. Hopefully NVIDIA has learned its lesson (one can pray), and will either add multiple 2x6 connectors in the future, or will at least add the circuitry back in to detect faults properly (they used to with the 30xx series back when we were using PCIE connectors only). This much power with such little headroom is a ticking timebomb (literally) for disaster, even if everything is working properly.
Don't let me scare you though, especially with the '80, I believe if you just double check that there are no kinks, you use a new cable, and check the contacts in the connectors, both from PSU side and GPU side, you should be ok.
