Extremely boiled down TL/DR: The author's invention is a spaced repetition system built into an essay, so instead of having the cards isolated, the cards are embedded in the text itself.
At a technical level, that's certainly innovative, but I'm doubtful about whether it's actually an improvement on classical SRS. In my experience, one of the most important things for an SRS deck is speed of reviewing: a given card should take less than 1 second to review and rate. This is necessary if you're going to maintain decks with tens of thousands of cards. I find my brain does a remarkable job of reconstructing the surrounding context, so having the cards embedded in the original text would just be a time sink for me, I think.
From reading earlier discussions of the quantum computing tutorial, I am pretty sure most of its readers do not even use classical SRS in the first place.
Yes, I was struck by the really exceptional and beautiful presentation/layout of OP's page. Perhaps the real contribution is less "build a better mousetrap" and more "market the hell out of mousetraps". If OP can show more people the light of SRS, that will be fantastic!
At a technical level, that's certainly innovative, but I'm doubtful about whether it's actually an improvement on classical SRS. In my experience, one of the most important things for an SRS deck is speed of reviewing: a given card should take less than 1 second to review and rate. This is necessary if you're going to maintain decks with tens of thousands of cards. I find my brain does a remarkable job of reconstructing the surrounding context, so having the cards embedded in the original text would just be a time sink for me, I think.