Amazingly (and the comments on his blog also seem to jump on this), he does acknowledge that you can do it with a package manager. There's advantages to learning how to build something like this from source.
Only in this case the learning effect isn't that great, because he doesn't explain the (to me) most confusing part: Why is the edit of the make file necessary? Isn't make responsible for choosing the right configuration settings for the current environment?
True, learning how to build things from source yourself is definitely useful, I probably wouldn't be using Homebrew if I wasn't comfortable with that first. It's definitely advantageous to be able to organise/upgrade everything via it though.