Nope, she is right. It is not about being "young and quick". It is about the biomechanics of his game.
Federer relies a lot on his serve, so faster courts help him. Aggressive serve returns are not natural to him; instead, he relies on his reaction to block serves back - and faster courts make block returns more effective. He has a 1HBH so low-bouncing courts allow him to be more aggressive off his backhand and slice less. He likes to hit wrist shots and half-volleys which faster, low-bouncing courts are well suited for.
Federer has most success at Wimbledon, Halle, Cincy, Dubai, and WTF. This cannot be a coincidence.