It is a very interesting write-up. A random thought I had while reading this: I feel like long-term, a system that schedules/"optimizes" the process of learning by reading/watching content and then engaging with this new content by taking notes and connecting those notes to existing knowledge could be more fruitful. Something akin to SuperMemo's "Incremental Reading", but not as focused on creating flashcards out of the material.

With traditional Q/A-style spaced repetition, I feel like accumulating a long list of isolated facts sometimes (I know, you can remedy this a bit by also quizzing connections, context, but I feel like the general tendency still remains).