Address follow-ups

Author: PIG208

peps/pep-0728.rst

@@ -290,10 +290,13 @@ the same rules that apply to ``extra_items=Never`` also apply to
 This will be further discussed in
 :ref:`a later section <pep728-inheritance-read-only>`.
 
-When neither ``extra_items`` nor ``closed=True`` is specified, the TypedDict
-is assumed to allow non-required extra items of value type ``ReadOnly[object]``
-during inheritance or assignability checks. This preserves the existing behavior
-of TypedDict.
+When neither ``extra_items`` nor ``closed=True`` is specified, ``closed=False``
+is assumed. The TypedDict should allow non-required extra items of value type
+``ReadOnly[object]`` during inheritance or assignability checks, to
+preserve the default TypedDict behavior. Extra keys included in TypedDict
+object construction should still be caught, as mentioned in TypedDict's
+`typing spec
+<https://typing.python.org/en/latest/spec/typeddict.html#supported-and-unsupported-operations.>`__.
 
 ``closed`` is also supported with the functional syntax::
 
@@ -600,8 +603,7 @@ be rejected even when ``extra_items`` is specified.
 
 Operations that already apply to ``NotRequired`` items should generally also
 apply to extra items, following the same rationale from the `typing spec
-<https://typing.python.org/en/latest/spec/typeddict.html#supported-and-unsupported-operations>`__
-:
+<https://typing.python.org/en/latest/spec/typeddict.html#supported-and-unsupported-operations>`__:
 
     The exact type checking rules are up to each type checker to decide. In some
     cases potentially unsafe operations may be accepted if the alternative is to
@@ -882,8 +884,8 @@ This is supported in `pyright 1.1.386
 revision is supported in `pyanalyze
 0.12.0 <https://github.com/quora/pyanalyze/releases/tag/v0.12.0>`_.
 
-This is also supported in `typing-extensions 4.13.0rc1
-<https://pypi.org/project/typing-extensions/4.13.0rc1/>`_.
+This is also supported in `typing-extensions 4.13.0
+<https://pypi.org/project/typing-extensions/4.13.0/>`_.
 
 Acknowledgments
 ===============