As long as you're using just the pihole YouTube shouldn't be able to detect it. The playback blocker is based on detecting common ad blocker extensions in your web browser.
If you use a YouTube app then yes, the ads don't seem to be able to be blocked. Browser based YouTube ads still seem to be able to be blocked by pihole
From my experience it's different servers, but it might depend on your location. It's the twitch ads that come from the same server as the video stream. Those are harder to block.
Also haven't seen any ads all this time but not because of pihole. I'm guessing it's because I also have DuckDuckGo Privacy Essentials and Privacy Badger installed as they block requests from "googleads.g.doubleclick.net"