I just tested it from my Android phone, where I'm not logged in to Itch, and I can confirm that the page is showing me an ad.
It's really strange, because even using an incognito account, I can't get it to show the ad on my PC, so I really don't know what's going on. Hopefully, someone can help us figure this out.
EDIT:
Okay, my PC isn't showing me the ad because Firefox is blocking Google Ads, but I don't know why that page has that advertising. I haven't read anything about Itch adding this type of advertising, and other pages don't seem to show anything. Could it be something to do with that developer's CSS?