It doesn't explain what "spaced repetition", "memory", "understanding", or "experiments" are either. It is written for people who already use spaced repetition,

It doesn't explain what "spaced repetition", "memory", "understanding", or "experiments" are either. It is written for people who already use spaced repetition, and aims to help them improve one aspect: writing prompts. It is not intended as an elementary introduction to spaced repetition, and so it doesn't bother to explain basic concepts. Your objection is a little like complaining that a computer science textbook aimed at post-grads doesn't bother to explain what a variable is. Some background knowledge is assumed.