If you know the type you need fewer checks in the jitted code, and you can optimise to native types.
If it helps python specifically, given that the types themselves are pretty dynamic, who knows. A python integer doesn't map well to a native integer etc. Python really isn't designed for performance, and retrofitting it is hard.
Makes sense. And that's rough, even the integers need dynamic memory. Maybe they can just use 64-bit static ints and throw an exception (or even crash) if you go oob. Probably quite rare that anything would rely on huge ints.
If it helps python specifically, given that the types themselves are pretty dynamic, who knows. A python integer doesn't map well to a native integer etc. Python really isn't designed for performance, and retrofitting it is hard.