Thanks for bringing this up. I suspect this is a case of there are always more things to do than time to do them. The request here was fairly open-ended too.
This book is open source now, and has been since last August. It is in the community’s shared hands to maintain it. That includes Apple, but others too if they want to contribute. If folks see areas they’d like to improve with suggested wording changes, feel free to propose them. The repository is also a good place to file issues.