But... I fully realize I'm doing this for fun. I wouldn't claim to anybody it actually makes me good at doing any of the things I'm "certified" in. So while I'm confident the author's approach is efficient and effective if your sole goal is "pass exam, obtain cert" - if there's any practical goal after that (e.g. "get employed and be good at doing this stuff"), I doubt this is a good approach. Maybe a good starter, maybe even not.
I'd be curious what's HN perspective?