Is Google selling sponsored banners inside AdSense?

Is this cross-promotion just a bug in the adsense system that is giving massive exposure to a few of Google's heavy advertisers?

I often see little quirks and sometimes bugs when setting up clients campaigns or researching their competitors but this latest issue seems to have a commercial benefit for both Google & Webprofits.  The issue arises when setting up your Google Adsense ads and you select to preview the AdSense unit. The standard preview is shown below to the right and is a clear example/test window with no working AdSense.

These preview units are match to you colour palette preferences, unit size and other settings such as custom font type.  What is interesting is that these preview windows are actually being reloaded to display live Google AdSense banners for companies such as Webprofits. There are 3 different types of ad unit you can choose but the Webprofit ads only show when it is image ads only or both text and image.

This would indicate that it is more than just a simple bug in the code and something targeted and possibly controllable by AdWords advertisers.  We decided to examine the code and discovered there was actually two different ad urls being displayed, the first is the 2 text link window shown to the right and the second is from the image at the bottom of this article.

The preview window ads links should contain the following code

Webprofits Ads

The other ad urls are what is shown when the image ad shown below is displayed inside Adsense or on an external website using Google Adsense, notice the similarities with a real AdSense url.

Webprofits ads showing inside Adsense contain

Url is similar to what is shown on a external website showing Google Adsense

It is also happening for multiple banner sizes so is it a new channel you can target within your Google AdWords campaigns or just a bug in the system that is giving massive exposure to a few of Google’s heavy advertisers? Since it is a live ad and likely generating clicks the advertisers must know that it is happening, but are they actively targeting the AdSense settings pages or is it part of Google’s automatic placement?