This is just prima facie untrue, and sure enough, even the article plainly states that 30 minutes of daily exercise will "probably" lead to 12 lbs of weight loss in a year.
Iff your diet doesn't change, which it often does because people often reward themselves after a workout, or a week of working out, or whatever. They tell themselves "I can eat this entire pizza, I've earned it", and the math gets fucked because of it.