How do they know that a bag is 10kg by looking at it? They do not have scales at the gate. If a passenger does On Line Check In (at home), no one from the airline will see them until they are in the departure gate. If they pull their wheelie case onto the plane and lift it into the locker, no one will know how much it weighs. Dimensions are more important if you want to fit 177 bags into the locker space of an A320 or 213 bags into an A321.
Will these baggage arrangements change the weight calculation for each passenger when the Flight Crew are Calculating the Take Off Weights?