When he is talking about weight penalty he doesn't mean an actual penalty given to a driver by race stewards. F1 drivers must meet a minimum weight (including equipment). Ideally a driver would be as close to the minimum weight as possible. Any driver weighing more than the minimum would be adding to the overall weight of the car, technically making the car slower if only by a few tenths or hundredths of a second per lap. So while technically not a "penalty", it is a disadvantage to weigh more than the minimum. Every last gram of weight makes a difference in an F1 car.