It does show you how to approach building a back-end in the first place, which I would consider to be quite instructive for someone who has never done it before

It does show you how to approach building a back-end in the first place, which I would consider to be quite instructive for someone who has never done it before. And it does separate the phases and still remains compact. Of course, once you have progressed to things like SSA, you might want to study something more complex. BTW, the current version of SubC has a much more interesting back-end and even uses AST-level optimization.