Can IBM enforce API copyright against BIOS vendors under this doctrine? Does this revive the SCO linux case? Who owns the copyright for POSIX/UNIX system APIs?

Can IBM enforce API copyright against BIOS vendors under this doctrine? Does this revive the SCO linux case? Who owns the copyright for POSIX/UNIX system APIs? What about cloud provider compatibility shims, e.g.: S3 reimplementations or Localstack? I am left with nothing but more questions about the broadness of this decision.