bpo-41584: clarify when the reflected method of a binary arithemtic operator is called (GH-22505)

(cherry picked from commit d02d824)

Co-authored-by: Brett Cannon <[email protected]>

Author: miss-islington

Doc/reference/datamodel.rst

@@ -2371,10 +2371,11 @@ left undefined.
 
    .. note::
 
-      If the right operand's type is a subclass of the left operand's type and that
-      subclass provides the reflected method for the operation, this method will be
-      called before the left operand's non-reflected method.  This behavior allows
-      subclasses to override their ancestors' operations.
+      If the right operand's type is a subclass of the left operand's type and
+      that subclass provides a different implementation of the reflected method
+      for the operation, this method will be called before the left operand's
+      non-reflected method. This behavior allows subclasses to override their
+      ancestors' operations.
 
 
 .. method:: object.__iadd__(self, other)
@@ -2773,6 +2774,6 @@ An example of an asynchronous context manager class::
    method—that will instead have the opposite effect of explicitly
    *blocking* such fallback.
 
-.. [#] For operands of the same type, it is assumed that if the non-reflected method
-   (such as :meth:`__add__`) fails the operation is not supported, which is why the
-   reflected method is not called.
+.. [#] For operands of the same type, it is assumed that if the non-reflected
+   method -- such as :meth:`__add__` -- fails then the overall operation is not
+   supported, which is why the reflected method is not called.