I think you're missing my point. Here's the UX.

1. I'm looking at primal but want to see only my closest friends content. (Primal knows this based on WoT and other signals I've given it over time - it's on them to come up with an algo that makes sense - I'm not manually doing anything other than using the app).

2. I change a setting on the feed page (takes less than 1 second).

3. My feed updates to only show my closest contacts.

4. I decide I want to see lots of new content. I change the setting. My feed updates again.

This can be made very very easy for users. The heuristics behind the scenes are doing most of the work, which is why no one has made this yet. It's quite complicated.

Also, there is the obvious issue with cold starts - your filter is shit for a while until Primal builds up enough info.