A WebmasterWorld thread has discussion around why the display URL differs in the “More Sponsored Links” section, when compared to the normal ads on the search results page.

WebmasterWorld’s Preferred Member, Rehan said:

The more link came to AdWords ads sometime in late 2004. Google then updated the design of that page in July 2008. Which is actually when the above changes happened.

You can read more about the more sponsored link at this Google help page.

Forum discussion at WebmasterWorld.