Muscle does not weigh more than fat. Muscle is denser, but 10 lbs of muscle weighs the same as 10 lbs of fat.
Hearing people continue to say this is very annoying.
If his goal is 255, and they want him to put on more muscle, and he currently weighs 254, then yes, obviously they would want him to tone up.
You could tell from looking at Sean Lee when he was drafted that he could put a lot more muscle on his frame. He looked like a high school kid. When he brings that physicality to his game, he is going to be that much better.