Right, I get that that's the theory, it's just that I've never personally seen it work out so well in practice.
I can imagine how it's extremely useful and rewarding for both partners if you have two very motivated people, and the better one is keen to teach and even genuinely open to suggestions from the "worse" one, and the "worse" one is keen to learn. That's the model for a good partnership that most people probably have in mind when they propose doing a project like this. I've just never actually seen a partnership work out like that -- it feels like it requires both members of the parternship have top ~quartile motivation/empathy/communication skills (which as you could imagine might end up being pretty rare among randomly selected CS students...).
In any case thanks for sharing your experience -- good to know that it actually can/does happen!