It is going to subjective and contingent on the mission of the document, and I’m not suggesting the manual should be changed.
I too would describe the manual as concise and approachable for OCaml beginners, and add that I find it to be appropriately scoped. However, the manual doesn’t contain elucidations on underlying concepts. As an example, chapter 5 of the manual (Polymorphic variants) makes no explicit reference to and explanation of row polymorphism, structural typing, and the process of refinement, which I find useful for understanding how polymorphic variants work. These topics are perhaps better suited to being expanded upon in a lesson.
An assumption could be made that lessons are geared towards developers familiar with strong static typing concepts, and if that is the case the lesson can be simplified significantly.
I think GADTs are a good example for how concepts in the manual can be expanded upon effectively. The manual provides a concise and beginner-friendly introduction to GADTs, and the longer treatment of the subject in RWO does a good job of tying the concepts together with examples in the narrative of a lesson. I’m the type of person that appreciates the sentiment behind RTFM, and I read the manual early in my OCaml journey, but it was RWO that made it clear to me what the motivation for and utility of GADTs was.
For another data point to consider, I appreciated the perspective @cuihtlauac introduced in his lesson on polymorphic variants from 2 years ago noting that LLMs hallucinate on the subject of polymorphic variants extensively. I forget exactly where it was noted, but the suggestion was made that this provides motivation for a lesson that treats the subject more explicitly. Two years later, I too find LLMs unreliable on the subject of polymorphic variants. On the subject of GADTs, however, LLMs clearly benefited from the text in RWO.
When the second draft is ready, I hope I can reach out to you for feedback on the lesson. It will be valuable to hear feedback that puts a downward pressure on the scope of the lesson.