For an illustration of the problem that this would cause, I did a quick search through Python’s own source tree. It already has various keyword names:

def seek(self, pos, whence=0):
def seek(self, cookie, whence=0):
def seek(self, offset, whence=0):
def seek(self, position, whence=io.SEEK_SET):

It is easy to imagine third party implementations also exist with a variety of keyword names. So I definitely think we should avoid changing the IOBase API because it will break backwards compatibility. And I think there is no good reason to add explicit keyword support to individual concrete classes like TextIOWrapper, in case it gives users the wrong impression about the general IOBase API.