[TMWNN]

>Students were definitely using Unix in 1975.

What I meant was that none of the various large multiuser systems in universities in 1975 ran on Unix. I imagine that most computer people probably vaguely think that Unix was the first large multiuser OS, and that all Berkeley, Stanford, and MIT students were using it, when neither is the case. If a random university student in 1975 wanted a computer account, assuming that such was available to a non-math/engineering/CS student, it would almost certainly have been on a batch system like your UMD example.

As I alluded to at the end, it's striking how within a decade Unix had clearly gained the momentum. Many (even majority) of non-batch systems in 1985 were likely still on VMS, RSTS, TOPS, or some other DEC OS, but those DEC-hardware sites were of course the first to move to Unix despite DEC's best attempts to prevent this.