I think calling the basics of the data model its 'precise implementation' is excessive. It's like complaining about having to learn the precise details of your display server because someone tries to explain to you how windows in a typical window manager work. The underlying model of git is not terribly complicated, is distinct from (but maps reasonably closely to) its implementation, and it makes understanding all the operations on a repo and working directory a lot easier, as well as making it easier to google for help if you get stuck or want to do something new.