Slate does everyone a favor by plainly stating something any serious—or, hell, any casual—home cook already knows: The cooking time listed on any given recipe is rarely accurate and is almost invariably an understatement.
The story's a good read, and it contains this journalistic gemstone: "But it was Chris Kimball, editor of Cook's Illustrated, who cut to the heart of it. 'Utter bullshit,' he said when I asked what he thought of cooking times." Kimball derides cooking times as "marketing," and that's certainly part of it. Calling any recipe the "30-minute anything" is both a lazy, easy headline and an enticing promise.
But there's more to it than that. Ruth Reichl, interviewed for the story, reveals that Gourmet's cook times come from the pro cooks who have drilled the recipe into the ground, not the fumbly, relatable "cross testers" who only cook it once. Well, yes, that might be a factor.
And beyond the realms of the cynical (marketing) and the process-related (expert testers), there must just be the fact that trying to do anything in the real world is inevitably going to be somewhat tough. You've got to scavenge your kitchen for specific dishes. Perhaps you have to wash specific dishes. Perhaps you're not the world's fastest dicer of carrots, or you get easily distracted by things as varied as demanding children, the need for some kind of immediate snack, or easily available alcohol.
Two sensible lines of thinking emerge from the story: It's time to drop the cooking times in favor of a ballpark estimate, or it's time to just quit the estimates altogether. Personally, I vote for the latter. The whole thing's a crazy subjective mess until you've cooked a few dozen recipes; at that point, your guess is as good or better than anyone else's.