The more this discussion goes on, the more convinced I am of my initial opinion. A matrix library doesn't belong in the standard library.
What is happening in the discussion is that each potential user who comments finds some related capability that is relevant to their particular needs. But the union of all those wishes is something substantially large... Maybe not NumPy large, but heading in that direction.
On the other hand, trimming such a thing to a bare minimum would mean that everyone using it would quickly hit limits that make it not really practical. Different limits for different people, but limits certainly.
If the purpose is JUST teaching a certain kind of course in linear algebra, that didn't seem like sufficient motivation for standard library, but it does sound like an excellent purpose for a third party library.