author here; yea the goal is to try and get the student to surpass the teacher, but if it can't, this is the best way to get close. For these contrastive losses, our intuition is that the model isn't trying to emulate the teacher so much as learning from the 'delta' between itself and the teacher
If you only emulate the teacher can you ever become an master?
It works in many competitive fields
Surely it needs more than just emulating the teacher, though, it would require exploring beyond those limitations?
But eventually your human mentor diminishes with age.