Spaced repetition [1], they send you questions over increasing time periods to consolidate what you learned in the long term.
I say that not as a physicist/mathematician looking down at the oiks trying to underastand this stuff, but as one of the oiks.
It's also by design that some of the questions are, as you say, laughably simple. It's to catch people who aren't properly engaging with the text as early as possible.
Nielsen and Matuschak are sensible to these sorts of critiques. Quantum country is part experiment after all and they've been learning, adjusting, and experimenting with what works best. If you want a bit of context of where they've come from and where they want to go, I recommend this: https://numinous.productions/ttft/