Do you mean that he has many times not understood what has been said, or that he has not understood that which has been many times said? If the latter, why should repeating something he hasn't understood make him understand it any better? If it doesn't make sense to him once, it won't next time either.
In any event, I don't think the relevant point (which I think is the one you think he hasn't understood) is that just because they have to be prepared doesn't mean they have to make the acquaintance of the rainforest (i.e. they don't necessarily have to be committed to paper).