I simplified things that would be too heavy to get into. The guide is not intended to teach everything about security -- that would be too much. The goal is to cover enough to give the reader a high level understanding. Once they have a basic understanding they can research more if they desire.
Can you tell me some of the "exotic details where defaults would be sane enough"? I can amend the guide.
Are you saying a public key can be used to decrypt data it encrypted? Or are you saying a public key could also be used to decrypt data that the private key encrypted?
You mention "server room". This guide is intended for a person running a simple server in their home. Hopefully SAs securing a large scale environment are not using information from GitHub. :/
I made some other updates to the guides that I hope address your other concerns?
Regarding your distribution agnostic comment, I do not see value in distribution specific guides on hardening. Sans a few edge distributions, most distributions are similar enough that the hardening steps are the same. It is okay to look for distribution specific documentation on how to install the distribution but it hurts the cause having distribution specific hardening guides.
Also, I want more folks to use Linux. Most distributions are so similar there is no value in having so many distribution specific guides -- all it does is create unnecessary confusion and steer potential prospective users away from Linux.