There is no ad in the app. it’s a bug.
If you want to re-create it. Follow a link to someplace like a GitHub project. You’ll notice a mobile ad banner at the top of the screen. Now go back to the voyager pwa interface. If you’re at the top and there are no other posts off of the top of the screen. Slowly swipe left or right and pull down. It’ll bring the banner from the previous page you visited into view.
I don’t think it’s the case here, I think this is just some PWA bug, but you could in theory get paid for showing the ad without the hassle of users complaining about being shown the ad.
I get this too, just for the developers FYI, not that I’m expecting anyone to fix a safari bug just to let you know of another side effect;
If you in a community and click on a post that has the hidden banner ad bug then when you click back to the post list you can’t scroll up or down. If you do the swipe right and pull down to show the offending ad and close it then you can scroll through the posts again.