Seems like a different focus, no? Aren't linear programming solvers a much narrower domain than general linear algebra libraries?

Correct, linear algebra and linear programming are two very distinct things. The latter is a widely-used optimization technique, and computationally depends on the former, which is a general mathematical framework for essentially all numerical computing.

That's code for linear programming (optimization) not for linear algebra

I asked because Faer describes itself as a low-level linear algebra library with a high-level wrapper, whereas good_lp describes itself as a high-level wrapper around many relevant low-level libraries.

Linear programming and linear algebra aren't the same thing.