That would mean the USB 4 controller is using 2nd M.2 slot coming out of CPU that was available on X670 boards and 16x slot is sharing bandwidth with 1 M.2 and x4 PCIe slot on board. Quite wierd design compromise.Because ASM4242 consumes four of those lanes and AMD, in their infinite wisdom, decided to (a) tie it to the CPU instead of the chipset, so that it consumes valuable PCIe 5.0 lanes even though it only needs PCIe 4.0 (b) release Zen 4 crippled in terms of PCIe lane functionality and stick to the same socket for 3 generations, meaning they have no leeway to increase that lane count (c) not upgrade the chipset from Zen 4 to Zen 5 either.
Edit: Gigabyte has posted User manuals for their X870 boards and here is the block diagram of how everything is connected.
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