I think what he means is that their Makefiles effectively start having a common API across projects, by having similar target names.
No need to use "all" if you put the default target first (see `default` subsection in the post).
> I'm also intrigued by their claim they used @ in the recipes, yet they never did.
Yea seems that got stripped out.
Still, this is a good practical example for using a Makefile. I'm a fan of this too.