gh-144161: Clarify additional immortalization in free-threaded build

Doc/c-api/unicode.rst

@@ -1750,9 +1750,12 @@ They all return ``NULL`` or ``-1`` if an exception occurs.
    :c:expr:`PyUnicode_CheckExact(*p_unicode)` must be true. If it is not,
    then -- as with any other error -- the argument is left unchanged.
 
-   Note that interned strings are not “immortal”.
+   Strings interned by this function are not :term:`immortal`.
    You must keep a reference to the result to benefit from interning.
 
+   .. note::
+      On the free-threaded build, all interned strings are :term:`immortal`.
+      This may change in the future.
 
 .. c:function:: PyObject* PyUnicode_InternFromString(const char *str)
 

Doc/howto/free-threading-python.rst

@@ -99,12 +99,12 @@ This section describes known limitations of the free-threaded CPython build.
 Immortalization
 ---------------
 
-In the free-threaded build, some objects are :term:`immortal`.
+On the free-threaded build, more objects are made immortal.
 Immortal objects are not deallocated and have reference counts that are
 never modified.  This is done to avoid reference count contention that would
 prevent efficient multi-threaded scaling.
 
-As of the 3.14 release, immortalization is limited to:
+As of the 3.14 release, this additional immortalization is limited to:
 
 * Code constants: numeric literals, string literals, and tuple literals
   composed of other constants.

Doc/library/sys.rst

@@ -1325,6 +1325,9 @@ always available. Unless explicitly noted otherwise, all variables are read-only
    Interned strings are not :term:`immortal`; you must keep a reference to the
    return value of :func:`intern` around to benefit from it.
 
+   .. note::
+      On the free-threaded build, all interned strings are :term:`immortal`.
+      This may change in the future.
 
 .. function:: _is_gil_enabled()