I had a couple of those boards. The full size slots aren't actually x8, because the CPU those boards support only have 24 PCIe lanes, and over half of them are just running USB, SATA, etc. The full size slots are so you can secure cards to the board, instead of running them zip tied to metal dish racks (like in the video i linked in my reply to your sibling comment: https://www.youtube.com/shorts/rTCInAXSzKA)