No, it's something along the lines of her "true potential" or "not being played offensively". Here's the thing - now bear with me as I reveal something that will boggle your minds - if Rosalina is powerful when used to her fullest potential, then that means anyone, such as Fox, Captain Falcon, Bowser, Zelda, etc. will be powerful when used to their fullest potential. If Diddy was played perfectly and everything was known about him, then that means he's still powerful to a Rosalina used perfectly. Are we assuming that Rosalina's the only character with an evolving metagame? Every character's metagame is moving at a different pace; Diddy, Rosalina, and Sheik's are moving quickly while Falco, Dr. Mario, and Ike's aren't in comparison.