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 first thing to realize is that the Sponsored Links search is unrelated to the keywords chosen by the advertiser to display the ad. Instead, the results shown are the ads that include the query words in the ad text. That's why you'll see only one or two ads at google.com/search?q=raccoon+squirrel (because it's not a great keyword to advertise for) but lots of them at google.com/sponsoredlinks?q=raccoon+squirrel (all of the ads shown contain those two words).So if the Sponsored Links search is unrelated to the keywords and shows just the ads that have the query words, that's why it uses the default destination URL for the ad rather than the specific ones for the keywords.
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.
