Your students certainly are an opinionated bunch, aren't they? They always are asking you questions, then doubting your answers!
In this case, I think that the student may be right. It's more than a change in attitude. In the example, the shy office worker who wouldn't ask for a raise does so, which would express a change in behavior. It would also display model or excellent behavior. From Dictionary.com: "excellent disposition or attitude in terms of vigor, courage, firmness of intent, etc."
With the caveat that the idiom means a change in attitude, behavior, and thinking, I believe your right as to when it would be used.