I am going to guess that the preparation the tutor is talking about consists of spending time thinking about and creatively solving high-level problems. I can't see that this would really have a down side in terms of intellectual development, honestly. I would see this kind of practice as having great value to his development as a mathmatician. It's not about whether he wins medals or if he even enters: it's about spending lots of time practicing thinking flexibly and creatively about dificult issues in math.
