I don\'t work with the Windows API much, but I\'ve seen it used there as well as occasionally in a codebase here at work.
Yup, they wanted to improve (Extend) the API and keep a similar name so it was likely that the programmer would move to the new version.
Notable is GetVersionEx() to get the Windows version, pretty painful for a while with a nasty chicken-and-egg problem.
The record keeper is the National Language Support team who have several ExEx versions, like EnumCalendarInfoExEx. Unsurprising, culture moves even faster than software. No ExExEx as of yet.