> but largely (functionally) indistinguishable from a UNIX machine when accessing it via teletype (glass or otherwise).

I disagree. I first sat down at a VMS terminal in a library in North Carolina when the OPAC broke and dropped me back to a prompt. I knew Linux passably well at that point but had never used VMS before.

I typed ls, tried dir, that worked, and finally tried help. In half an hour I was investigating the university's network. It was a remarkably easy system to get oriented on. Conversely, no one can be expected to get anything vaguely comparable when sitting down unattended at a unix shell for twenty minutes.