It is a fantastic guide, as I have always been hesitant to trust the "passed" of the SMART test.
I'd say you're right not to trust such things. A single piece of S.M.A.R.T. data in isolation seldom tells you much. Metrics derived from smartctl along with metrics of how the disk is performing are far more useful. Going further depending on your environment if you have a large enough deployment of a particular drive you may also be able to infer other drive failure characteristics.