you are not being interrupted. your partner is thinking with you

As the many examples in that discussion show, this is your subjective experience, with others build different than you.

To me, those two sentences side by side are in complete contradiction with how I experience the world, where the knowledge of a persons attention is distracting, like a glaring light.

But, for learning a new language/framework/codebase, I think it would work very well. The quickest, and most enjoyable, "ramp ups" I've ever experienced were just sitting next to someone and bouncing questions off of them as I explored.