Yah atproto auths moving data from the pds to the index, similar to like https, but they missed authenticated distributed data storage somewhere along the way. Why is that, I wonder?
In practice, this can be annoying and there are alternatives for people who write software that doesn't bother to check signatures.
Relying on https alone means you kinda have to get the data from the original website to know that it's authentic, and you can't prove it to anyone else other than by sending them the URL so they can check for themselves. (I mean, technically. In practice, people will trust quotes or screenshots even though they can be faked.)
But you're right that the screenshot proto and the copy and paste proto are quite successful as a distributed system these days.
Hubble is starting to come online, which is a network cache. With excellent storage and runtime characteristics, cheap to run. I'm not sure if this is in the same https://microcosm.blue banner-head, but the same developer, as another incredibly fantastic network service that's open for use, that's open source, that other people can also run themselves. https://atproto.com/blog/introducing-hubble-a-public-mirror-...
I agree that yes the PDS's hopefully start doing more mirroring too. It'd be nice if they would themselves also attest that they have seen it too.