Yes, but the tutorial isn't suggesting the reader go do proofs. Instead he says these more advanced topics are unnecessary. I said: their necessity is not appar

Yes, but the tutorial isn't suggesting the reader go do proofs. Instead he says these more advanced topics are unnecessary. I said: their necessity is not apparent until you try doing proofs; but then you see them everywhere like a man with a hammer sees nails. Mind, his approach may well be the correct one for the context, but you're saying he's doing things my way, which he's not.