I fail to follow Cal's argument. It seems that he is abandoning his "digital detox" doctrine towards privacy.
If the issue with social networks is the time we waste on them, why would an algorithmically generated feed be less addictive than a social network feed?
I didn't read that Cal is arguing that one should use TT over FB.
I think he's just pointing out that FB's change into a TT-like graph isn't in their wheelhouse. FB built up a social graph. TT has built up an attention profile. Though they look similar, Cal is saying they are different. FB will be starting from the near bottom and years behind.
I don't think it matters much whether it's in their wheelhouse or not or whether they succeed or not. What matters is that transitioning away from the social graph is abandoning their moat, the very thing that keeps them a monopoly in social media. Once that's gone it'll be a level playing field and they are unlikely to survive for long.
A graph of details about rich media is still, in some sense, a social graph.
Rather than documenting: who do you know? when did you meet them?
Capturing: what do you know? when did you learn it? who did you learn it from? what do you call it? how should it be presented? And so on...