There are particular mentoring objectives that you can hit with it, and there is value in bouncing ideas off another person, but I don't need to sit in front of a computer screen for the latter.
I often go on remote calls with people and our task is to implement something while also training the person or giving tips on how to do it in the future while answering any questions they have in real time (related or not).
So it's more of a 1 on 1 teaching gig for an hour or 2. Not 8 hours of pair programming every day full time.
Like to this day, I have never seen any reproducible strong evidence provided that pair programming is beneficial. And I don't know if I would call the occasional ad-hoc (unstructured) "pairing" anything other than what a normal person would call it: "two people collaborating like normal fucking human beings."
But if there is evidence that 2 is better than 1, why is 3 or 4 not even better?