Rock 5B+ M.2 B Key connector support SATA Expansion Card?

@ChenJaly @Bruce_Costello may I kindly clarify Rock 5B+ M.2 B-key capabilities?
There are mixed messages regarding this. This post states

raised 2242 B-key slot on front with PCIE 2.1 x1 lane

so is PCIe x1 lane actually available on B-key or USB signaling only or both?