Yeah so the reason this doesn't work on Intel platforms is actually because on LGA1700, Intel moved away from x8+x4+x4 to x8+x8. Not sure WHY they did this, but LGA1151 and LGA1200 had support for x8+x4+x4. As to why they can't do x4+x4+x4+x4, I believe it has to do with Intel limiting that feature to their HEDT and server platforms, as those platforms actually do support x4+x4+x4+x4. Or maybe they thought most power users would be using a graphics card, so have the x8 on the first slot, don't spend extra engineering on splitting the first x8 down to x4+x4, and there could be cost savings there, but this is also why on mainstream Intel platforms, you could only use 3 out of the 4 m.2 slots on the hyper m.2 PCIe x16 cards for example. AMD actually supports x4+x4+x4+x4 on even their cheapest A620 chipset boards, even on the AM4 boards as well I think, as long as the BIOS manufacturer adds bifurcation support.
NGL, 1500$ to have a PCIe card that can't even have all slots working without a motherboard that supports bifurcation, and on top of that specifically x4+x4+x4+x4... this should not be 1500$. This is probably a 500$ card at best because it is PCIe 5.0 and sure, it does have the other lanes from the Broadcom chip, but still. It is UNNATURALLY F*CKING DIFFICULT to find a PCIe m.2 carrier card that can split an x8 or x16 signal down to x4 without bifurcation from the motherboard. I have an 11900K and Maximus 13 Hero in my VM/NAS PC, and I have been looking for potentially adding a dual m.2 PCIe card in that first slot as I already have an x4 SSD in the second slot, all other slots (except for the x1s, which I intend on populating later) are filled, and the board splits the CPU lanes to x8 in first slot, x4 in second slot, and x4 in one of the m.2 slots, so I can't split the first x8 into two groups. Every single card has the stupid bifurcation requirement, or doesn't support PCIe 4.0 at least. But of course, why would they lower the price? It's not like the people that can take full advantage of this card have the bifurcation dilemma anyways since they are likely using them in servers where they have full out x16 slots that can bifurcate, on top of thunderbolt/network cards for stupid fast NAS use.