>Bell Lab's Plan 9, for example, did so in part in the late 1980s.

Plan 9 did not support forking to remote machines and was not a single system image system. Its support for running a program on a remote machine was a completely userspace program.

If you say Plan 9 was an example of teleforking, then so is ssh. That might be a reasonable categorization, but both Plan 9 and ssh are very different from LOCUS and other SSI systems.