Ah, OK. Thank you, ED.
I noticed it as I Customised an empty menu. The default choice appeared at the end of my customized menu, on clicking it nothing happened. So I turned it off (for that menu, I thought) and it disappeared from all the others.
So, Plan B would be an FR / Nit Pick: If the default menu is empty, do not display the "Default menu" choice at the end of the customised menu.
Raised here:
http://forum.cockos.com/showthread.php?t=107010