Found a temporary fix
According to this, it’s a lenovo BIOS issue, something about secure BIOS settings and disabling WMI, which caused configuration issues with nvidia dGPUs. Rolling back the BIOS fixed this link speed issue, though I do not know yet if a later bios has fixed this issue or not.
Lenovo’s Chinese support site has old BIOS packages available. Per the linked post, googling ‘[BIOS Ver.] lenovo cn’ should get you the site.
I will consider this the solution for this thread for now.
EDIT: Latest BIOS (J2CN61WW) does NOT fix this issue. Anyone know how to escalate this to Lenovo or get it to their BIOS/Legion team?