I'm surprised at the negativity here. The framing/headline could be a bit better (it's less logic and rather a taste of the "art" of punchy, emotive typography, the softer intuition side of things) - but as a working corporate design manager, his rationale checks out for basic projects that working designers are presented with.
Of course, therin lies the split between engineers and designers. :) Each to their own, ultimately, and there's different places for both.
TFA is a self-described "tutorial" that doesn't actually teach you how to make similar decisions in a different context. Having gone through this, I am no better equipped to select typefaces and configure spacing on my next side project than I was before I started. It's a complete and utter waste of time.
There's no "why", only some vague and useless "we can do better"-type hints without explaining why 26-px line height is better than 27.
Of course, therin lies the split between engineers and designers. :) Each to their own, ultimately, and there's different places for both.