I'm not sure who the intended audience is; for a casual reader who'll never write code, it's probably way too detailed. For an engineer who needs to understand mechanisms, it's too abstract. We need scripts (to be fair these are given), transactions, utxos and signatures, and we need the sequence of steps, between the parties. So the 'Payment diagram' on 'payments' is good, e.g.

It's always great to have abstract descriptions to gain insight, but for a new and complex system that has to come after writing the *exact* mechanism. Imo.

there is no spec