Writing specifications, and knowing which items in the roadmap bring the most value to the greatest numbers, are hugely different beasts. I definitely took the PR-driven approach to mean identifying those 2 items, even if taken by themselves (without the rest of the roadmap) they are meaningless. This is a massive, valuable skill to have...and one I'm not sure how to acquire. Don't know if this convinces you, but the article really spoke to me.