If he's higher than average in head circ. and height too, I would say his weight fits his growth of the rest of him. Honestly, I would take what she says with a grain of salt. If he was that weight, but average height and head circ, then I might possibly be a tiny bit concerned, but otherwise, I think it sounds like you have a healthy and happy little man (or not so little!) on your hands.
There has to be someone on the bigger and smaller ends of these scales. Sounds like yours in on the bigger end of normal.