DOCS: update simple_prompt phrasing.

Closes  #14402

IPython/terminal/interactiveshell.py

@@ -225,11 +225,14 b' class TerminalInteractiveShell(InteractiveShell):'
         help="""Use `raw_input` for the REPL, without completion and prompt colors.
 
             Useful when controlling IPython as a subprocess, and piping STDIN/OUT/ERR. Known usage are:
-            IPython own testing machinery, and emacs inferior-shell integration through elpy.
+            IPython own testing machinery, and emacs inferior-python integration through elpy.
 
             This mode default to `True` if the `IPY_TEST_SIMPLE_PROMPT`
-            environment variable is set, or the current terminal is not a tty."""
-            ).tag(config=True)
+            environment variable is set, or the current terminal is not a tty.
+            Thus the Default value reported in --help-all, or config will often
+            be incorrectly reported.
+            """,
+    ).tag(config=True)
 
     @property
     def debugger_cls(self):