There was some discussion a while ago on python-dev about it.  AFAIR the outcome was that using "bytes *strings*" should be avoided because bytes are bytes, and not strings (until they get decoded at least).  Using 'string' for both might lead people to think that there are two kinds of strings, bytes and Unicode (like in python 2) while they should think that there are only Unicode strings and they can be converted to a bytes object (or simply to 'bytes').