Artists draw with all kinds of strange gear, especially if it's all they have and they've gotten used to it. That said, in the long run it's better to begin by learning to draw with the normal implements. If technically accomplished professional artists think you should start by learning to use a pencil, pen, brush, and stylus, there's probably a reason for it.
The shape tools aren't good enough to substitute for real drawing.
Tell your friend to master the basic techniques first. After that, if he wants to use shape tools or draw with a gaming mouse, fine -- let him do it. But if that's where he starts, his technique is always going to be limited.