In a more recent article Michael Nielsen and his co-author Andy Matuschak have adjusted their thinking somewhat:
https://numinous.productions/ttft/“One of us has previously asserted (Michael Nielsen, Augmenting Long-Term Memory (2018)) that in spaced-repetition memory systems, users need to make their own cards. The reasoning is informal: users often report dissatisfaction and poor results when working with cards made by others. The reason seems to be that making the cards is itself an important act of understanding, and helps with committing material to memory. When users work with cards made by others, they lose those benefits.
Quantum Country violates this principle, since users are not making the cards. This violation was a major concern when we began working on Quantum Country. However, preliminary user feedback suggests it has worked out adequately. A possible explanation is that, as noted above, making good cards is a difficult skill to master, and so what users lose by not making their own cards is made up by using what are likely to be much higher-quality cards than they could have made on their own. In future, it’s worth digging deeper into this issue, both to understand it beyond informal models, and to explore ways of getting the benefits of active card making.”