From the same article above and of course the weight could just as well be on the rider and not the bike, it's only about the aerodynamics:
What if the reason Mr. Heavybike’s bike is heavier is because it is more aero?
Let’s suppose that Mr. Heavybike is only 1% more aero on his bike. To achieve that, he would only have to reduce his frontal surface area by 1%, from 0.5 square meters to 0.495 square meters. This is pretty easy unless Mr. Heavybike’s position is already very carefully refined. A 1% reduction in aerodynamic drag will increase his flatland speed to 25.03 mph. That’s faster than Mr. Lightbike’s 24.99 mph. But what if Mr. Heavybike borrowed his machine from Mr. Reallyheavybike. How much would his bike have to weigh to soak up a 1% aero advantage? The answer is about 11 pounds more than Mr. Lightbike’s machine. So, Mr. Lightbike is stylin’ at the start line with a 17.6-pound bike, but Mr. Heavybike will match his performance on a 29-pound bike if he’s only 1% more aero.