The ads still appear in the facebook feed but clicking them results in a “this site could not be found” or similar error, is how I understood it to work. I know the PiHole basically makes it so the routes from “whateveradwebsite.com” end up not resolving to an IP address. I’m not sure how FB is serving them; so the text/image content might be coming from an FB server and the link is just an ad URL with a bunch of tracking info on it.