Installing HSF card is not just "installing the card itself". Just like a card with a radiator you also have to install power cables and secure the card. And if the heatsink is big enough and it's not installed vertically then it will also need to be reinforced with a support.
I specifically mentioned "fitting the radiator" as an extra step compared to standard air cooling. Connecting power cables and screwing the case screws are common to both sides of the equation, so we can safely discard them from the comparison.
As for the support, being a quad-slot design most likely fares better than standard double-slot ones. Thicker beam = less bending (on all axes). And the cantilever support at rear would be definitely designed to be more than adequate at handling shear and bending stresses.
More wires for AIO is a myth and depends entirely on the manufacturer. It's possible to combine all wires into one like Arctic does with theirs instead of the rats nest Corsair ships with. It would be even possible to make a solution where the fans/pump take power from the card itself with no external power needed.
I wasn't saying that more wires is bad. That was Ferrum Master's argument. I merely pointed out that aircoolers have less wires. This isn't a myth. Except for the case where radiators don't have fans (why?), a typical watercooler has two sets of wires because it has two electrical components: pumps and fans, compared to only fans in an air cooler.
Indeed, OEMs can be crafty with their wiring like you proposed, but then they'd be losing one of the advantages an AIO has: Ease of replacing (radiator) fans.
Have you seen latest HSF designs? Nvidia FE's are over engineered with tens of different size screws and glue. Taking apart HSF card may end up being much more of a hassle than removing a waterblock. And why would you need to remove the entire AIO to dismount the PCB from the block? Assuming the tubes are long enough there is usually no reason to remove the entire AIO even for repasting.
"Assuming tubes are long enough."
They rarely (never?) are. And for good reason. Longer tubes add cost and reduce performance.
I've seen someone who worked with an (CPU) AIO with the rad still mounted. This ended up putting too much stress on the joints and it ended up leaking.
The 4000 gen cards don't use glue. Disassembly of 4090 FE cooler can,
to quote W1zzard: "be done in a few minutes."
And similarly to the wires point, repasting wasn't something I mentioned (or even believe to be an issue worth mentioning). I don't believe anyone should need to take apart a card unless they're modding or something.
No there are more cases against HSF's. Like weight. Complexity. Dimensions inside the case (blocking M.2, SATA and other motherboard slots or ports). Some manufacturers even had to engineer a solution to release the PCIe clamp with a separate button because people could not reach it with massive aircoolers in the way. Also HSF may be harder to clean because of the massive finstack that accumulates a lot of dust.
Valid points. But I'd argue that motherboard ports aren't typically hot pluggable (except for SATA). So an aircooler would only affect the order of fitting components/cables at install time.
[Disclaimer: Not saying the next in defense of aircoolers, just ranting] Whoever though placing m.2 slots bellow PCIe slots should be banned from ever designing a board. Stupid, stupid placement that ends up forcing users to either leave the slot unused or suffer shitty temps!
