For me pair programming accelerates development to much more than 2x. Over time the two of you figure out how to use each other's strengths, and as both of you immerse yourself in the same context you begin to understand what's needed without speaking every bit of syntax between each other.
In best cases as a driver you end up producing high quality on the first pass, because you know that your partner will immediately catch anything that doesn't look right. You also go fast because you can sometimes skim over complexities letting your partner think ahead and share that context load.
I'll leave readers to find all the caveats here
Edit: I should probably mention why I think Chat Interface for AI is not working like Pair programming: As much as it may fake it, AI isn't learning anything while you're chatting to it. Its pointless to argue your case or discuss architectural approaches. An approach that yields better results with Chat AI is to just edit/expand your original prompt. It also feels less like a waste of time.
With Pair programming, you may chat upfront, but you won't reach that shared understanding until you start trying to implement something. For now Chat AI has no shared understanding, just "what I asked you to do" thing, and that's not good enough.
