We have people following multiple development paths, though. If we write our documentation the way you suggest, that closes out people who are using other methods -- people who are self-hosting their dev environment, for instance.

Which is not to say that some things can't be clearer, but there is always going to be ambiguity in our docs, and if your learning style doesn't work well with that, this might not be the starter project for you. (Generalized 'you' there, not you in particular.)