I don't think that anyone would lose understanding when they practice something more. However, I do think that focus on rote learning can discard a lot of conceptual information that's important, and in addition I know from experience that gifted kids can quickly stop focusing when the material's boring.
I think it's okay for gifted teaching to be more conceptual. I think regular teaching ought to be that way, too.

I agree with you that no one should be given such a message. What a poor teacher she must have.