In the case of the phone, one simply sees recipient of call, duration etc, regardless of how much information was exchanged. The phone I'm calling is arguably analogous to the server I request a page from, in the metadata context.
I'd argue browser history is significantly richer in some regards due to this. It's not unheard of for user identifiers to appear in URL paths either - try visiting https://news.ycombinator.com/user?id=<HN user name>... In my Chrome, that's instantly in the history file with my username.
I don’t know anything about this system, but the fact that screen shots are not ultimately stored on the user’s PC doesn’t mean anything if the content has already been classified and indexed. It will be fished.