Clarify discussion for 4398

Author: jwakely

xml/issue4398.xml

@@ -24,11 +24,13 @@ template<> inline constexpr bool enable_nonlocking_formatter_optimization&
 </pre></blockquote>
 </blockquote>
 <p>
-However, formatting an adaptor requires formatting of the underlying range, and we disable 
-the nonlocking_optimizations for all ranges.
+However, formatting an adaptor requires formatting of the underlying range
+in terms of `ranges::ref_view`, and we disable the nonlocking_optimizations for all ranges, including `ranges::ref_view`.
 <p/>
-This problem does not occur for the `flat_set`, `flat_map` adaptors, which are also ranges, and 
-do not have a specialized formatter.
+This problem does not occur for the `flat_set`, `flat_map` adaptors, which are
+also ranges, but unlike `stack` etc. they do not have a specialized formatter.
+They use the `formatter` specialization for ranges and we already disable the
+optimization for that formatter.
 <p/>
 The proposed wording has recently been implemented in 
 <a href="https://gcc.gnu.org/pipermail/libstdc++/2025-October/063758.html">gcc's libstdc++</a>.