The vignette ads are also mobile only and are full screen ads that appear between the page loads on your site and can also be dismissed by your users. You may be able to see them on the page-level ...

Here’s what you get: New photo effects and tools, such as vignettes, stencil overlays, and shadow and highlight adjustments. Overlays let you place stencils over your photos for creative effects ...

The effect as described in Google’s blog post does not exactly apply to AdSense Page-level ads. There are two types of Page-level ads: anchor/overlay ads and vignette ads.