Anthony Higman shared that Google is experimenting with varied headline sizes with ads, where H1 and H2 remain regular-sized, while H3 appears in a smaller font. This change aims to improve ad readability and create a better user experience by distinguishing primary and secondary messaging.

It’s interesting to note that the second ad features two main headlines along with a smaller additional one. Could it be the third headline?
Let’s remember that Google recently tested callouts as a subheadline.