This seems like a great idea but should be used very sparingly. Your "bored genius" isn't necessarily a great teacher, and that's not their job anyway. I've found you're better to give them more challenging options. If they want to be bored that's on them; if they pursue it they'll likely do it independently.

So, really no benefit for the genius and all the benefit for the weaker ones and the teacher who does not have to run their patience thin.

No, I think giving the genius a challenge that they came for is the best way to go about it. If you have none, that's fine, let the genius discover things on their own, they were almost certainly doing so anyways and its best to not get in their way.