Those people/use-cases don't care about the GIL. When you're doing anything numerical you're calling into Numpy, Pytorch or Polars anyways and those libraries make use of multiple threads and drop the GIL.

So yes, you can do Matmuls to your heart's content in one python thread and wait for file i/o in another thread without ever running into issues with the GIL. I'd even say if your Python Interpreter isn't bored waiting for stuff to happen, you're doing it wrong.