I cannot tell if these are:- new YouTube ad-units, or - bizarre / sneaky advertiser units
... but they are appearing more and more across the Google AdSense network. The below screenshots are taken directly from advertisements appearing on my blog:
1. This is what a standard YouTube unit looks like: big play button in the upper right corner and the standard YouTube footer beneath (play, sound, progress bar and "Ads By Google logo").
2. This is an example of a different "YouTube" unit... whether official or not: an image, a smaller Play button that prominently displays "YouTube.com" and text that looks like a text AdSense unit.
3. The unit is fishy for three reasons: A. When clicking "play", it goes to the YouTube URL rather than playing in-line, and B. The unit's size is slightly off - if you highlight through the text, you notice that it scrolls within the unit (see the difference between these two screenshots) C. Google is very particular about showing the "Ads by Google" graphic... which is hidden unless you scroll down
Here are two more examples... suggesting that it is in fact a new unit: