Google is testing that new large ad and organic label headers design but this time having the header stick to the top as you scroll. We've seen Google test sticking the ad labels as you scroll down the ads before but not in this new design.
Gagan Ghotra posted this example on X, which I cannot replicate, here is a GIF of his video cast of it in action:
I don't like this new large header design but I do like sticky headers like this, so you know you are scrolling through ads or not scroll through ads.
Here is a static image of this from Gagan:
Forum discussion at X.