Yes, that's what I said.

If you are writing performance sensitive code that is not covered by a popular Python library, don't do it unless you are a megacorp that can put a team to write and maintain a library.

It isn’t what you said. If you want, you can write your own matmul in Numba and it will be roughly as fast as similar C code. You shouldn’t, of course, for the same reason handrolling your own matmuls in C is stupid.

Many problems can performantly solved in pure Python, especially via the growing set of tools like the JIT libraries I cited. Even more will be solvable when things like free threaded Python land. It will be a minority of problems that can’t be, if it isn’t already.