What possible use is a PCI-E x1 SATA III controller?

HDD Caddy SATA 3 Second Hardisk Slot Laptop mm slot sata 3 Four-channel SATA III PCI-Express controller with two internal SATA ports and two slots for SATA disks Standard & Low profile slot city app In this video, we will take a look at SATA SSD and NVME slot and their differences

slot ovo 3 slots where most boards disable 2 of the sata ports, asrock disables the 3rd pcie slot in the case of the two boards you're looking