My guess is that Turing thought that you wouldn't need to make such a choice, and that a robot that could analyze the intricacies of medical diagnosis could surely be able to talk about the weather. It's much like you don't have to make a choice between your program being able to do medical diagnosis and the program having a full-color graphical interface (or even a touch interface on your phone, these days).

In other words, I think that Turing was simply wrong on this point. Though, it's not hard to imagine a future where it becomes cheap to make a program pass a Turing test, changing our expectation of what the user interface for a computer should be like.