Anchor ads now support a larger range of screen sizes. For sites that have anchors turned on, anchor ads will soon start to appear on wider screens such as desktop. Our experiments show that anchor ads perform well on wider screens.
If you'd prefer not to show anchors on wider screens, you can turn this option off using the new "Wide screen" control in your Auto ads settings. Note that wide-screen anchors won't start serving until after July 19, 2021.