I think this, or a future version of this, would have real potential.
I'm thinking about this in terms of the navigator-pilot pair programming approach, and believe that as a senior, if it's even half-as-good as working with a fresh out of uni hire, then it could have real value. When there's a piece of code that I would like written, when I have good test cases in mind, but would prefer to offload it on someone, I could perhaps write the test cases and function signatures (maybe with the bot's help), get the bot to fill in the blanks until it passes the tests, and then give it direct feedback on how to refactor the code.
I've signed up for the waiting list and am excited to try this out.