The thing is, I don't think it's necessary. This guide doesn't aim to add anything that Pro Git or Git Immersion don't already provide. I've tried to avoid adding additional noise to the mountains of Git documentation out there unless I feel there's real value being added, which I hope is the case with my own series of Git-related blog posts (http://pivotallabs.com/users/khicks/blog).
Agree with your amends to op but not with your last point. This article has flaws but has some good parts. If corrected it could be useful for users with some experience of git but want a deeper understanding, and have no patience for a very detailed textbook.
I think that it would be interesting to reread this after it's been worked over by someone to better represent the way that Git actually works.