How to apply @enum.nonmember?

Question

I was trying to come up with a use case for the new @enum.nonmember decorator in Python 3.11. The docs clearly mention it is a decorator meant to be applied to members. However, when I tried literally decorating a member directly:

import enum


class MyClass(enum.Enum):
    A = 1
    B = 2

    @enum.nonmember
    C = 3

this results in an error as:

Traceback (most recent call last):
  File "C:\Program Files\Python311\Lib\code.py", line 63, in runsource
    code = self.compile(source, filename, symbol)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Python311\Lib\codeop.py", line 153, in __call__
    return _maybe_compile(self.compiler, source, filename, symbol)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Python311\Lib\codeop.py", line 73, in _maybe_compile
    return compiler(source, filename, symbol)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Program Files\Python311\Lib\codeop.py", line 118, in __call__
    codeob = compile(source, filename, symbol, self.flags, True)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "<input>", line 9
    C = 3
    ^
SyntaxError: invalid syntax

However, if I had declared an atribute as a property or a descriptor it also wouldn't become an Enum member... So how, when and why do you use @enum.nonmember?