What does pihole block that ublock doesn't?
App ads, all the trackers from Netflix, Plex, Sonos, etc.
Because, e.g., Apple has official support for allowing apps to easily use DoH/DoT for their connections: https://developer.apple.com/videos/play/wwdc2020/10047/
I would be mighty surprised if this was the only such mechanism
I can view the logs in AdGuard Plus, the only time I see an ad in Words With Friends or Flipboard on my iPad is when I'm off my Tailscale VPN (which goes through AGP). Apps that serve their ads directly, like YouTube, are not blocked sadly. But there are multiple workaround apps for that on Android atleast.
Also some apps don't work with the tracking blocked, like Fox Sports, but I just whitelist the minimum amount needed on a per device basis.
Test this page on your phone without an ad block and see how it goes:
Because when adding telemetry to the app, do you really think they go out of their way to make it easy to block?
You don't get everything from a Google or Facebook app, just use a cracked version of their apps in those cases. But most of the blocking is better than none.
You can also just continue to use Chrome and be tracked across the internet. Helps pay for those of us that block it.