PEP-654: state that interior nodes are checked for match in subgroup/…

…split (GH-2113)

pep-0654.rst

@@ -218,9 +218,13 @@ contains only those exceptions for which the condition is true:
    >>>
 
 
+The match condition is also applied to interior nodes (the exception
+groups), and a match causes the whole subtree rooted at this node
+to be included in the result.
+
 Empty nested groups are omitted from the result, as in the
 case of ``ExceptionGroup("three")`` in the example above.  If none of the
-leaf exceptions match the condition, ``subgroup`` returns ``None`` rather
+exceptions match the condition, ``subgroup`` returns ``None`` rather
 than an empty group. The original ``eg``
 is unchanged by ``subgroup``, but the value returned is not necessarily a full
 new copy. Leaf exceptions are not copied, nor are exception groups which are