Why would a PCIe x16 slot be limited to PCIe x1 card?

Why would a PCIe x16 slot be limited to PCIe x1 card? pciex1 slot This video explains everything you need to know about PCIe slots, including PCIe slot What pciex16 slot configuration I cut open the back of a x1 slot on my motherboard to allow me to fit a full size GPU

pciex16 slot configuration PCIE X1 SLOT PCIE X1 GOLD FINGER 20201007 U98 增加EPAD 20201007 U98 Pin17 改open SMB_CLK_RESUME1 SMB_DATA_RESUME1

pciex1 slot The PCI-E expansion riser card adapter is designed to convert 1 PCI-E 1X slot into 3 PCI-E 1X slots The 3 PCI-E 1X slots could connect sound card, graphics What happens is that if you have disabled onboard LAN, the upper pcie x1 slot stops workingdetecting cards, and this change also seems to brick