I've been talking about the case that you're logged in with a Piped account, which makes your subscriptions and playlists become stored at Piped's server.
Piped does more than just proxying at its backend, the only thing that you could really call to become proxied are thumbnails and video playback.
There's also https://status.piped.video which allows you to view the uptimes of all public instances, and their might be added something like that to the instances api in the future too.