If you run Pi Hole, AdGuard Home, or any other network level adblocking services on your network, iOS 27's Connectivity Assist gets around these block lists in iOS applications.
That's because the cellular network it "Assists" with isnt blocked, and iOS treats your blocked traffic like it needs a workaround from the cell network.
To fix this, go to the settings for your specific Wi-Fi network and disable Connectivity Assist.
Connectivity Assist improves your connection by using cellular data when this Wi-Fi network is unreliable or slow. If you're concerned about cellular data usage or you use an ad blocker, you may want to turn this off.
That's because the cellular network it "Assists" with isnt blocked, and iOS treats your blocked traffic like it needs a workaround from the cell network.
To fix this, go to the settings for your specific Wi-Fi network and disable Connectivity Assist.
It sounds like "Connectivity Assist" should really be called "Ad Assist".
Luckily you can turn it off