Well, the terminology in these docs is not very precise and helpful.
There are two things here:
- the buffer /struct/ a.k.a Py_buffer, which can only be used from C
code and using the dedicated "new buffer API"
- the memoryview, which is a Python object (a PyObject *) wrapping a
buffer struct; as a PyObject *, it can be used everywhere a regular
Python object is expected (whether in C or in Python)

Then, as you point out, there's a third thing: the old "buffer" object
from Python 2.x; but it should not be mentioned at all in the 3.x docs,
since it's completely gone.

Endly... to be honest, I don't understand what the sentence you've
quoted is supposed to mean :-(, so I don't know how to correct it.