I didn't know about this project, so I took a quick look around.
I didn't see any mention of Telemetry or Metrics, but I assume they can use this:
After starting Tails and connecting to Tor, Tails Upgrader automatically checks if upgrades are available and then proposes you to upgrade your USB stick. The upgrades are checked for and downloaded through Tor.
Don't worry, the authorities already have the slightly less convenient way to backdoor things.
Why make a fake release when you can just include it in the real release for the price of just a little coercion?
You could host the release on the police servers and they still couldn't get a client with a pinned public key to download a malicious version, because releases are signed.
That said, while TAILS takes security seriously, you shouldn't just expect all package managers to update themselves securely. This is why you want to avoid these new tools that don't care about security, like flatpak, snap, brew, chocolaty, docker, pip, npm, etc