To me, the only difference between urlsplit() and urlparse() is that urlsplit() does not treat parameters following a semicolon specially. The documentation tends to agree with this view. So whatever exceptions are raised by urlparse() should also be raised by urlsplit() for consistency.

Also, I doubt it is worth worrying about the finer details of splitport() or whatever, because they are meant to be deprecated and not used externally, except for backwards compatibility.