The Parity Principle 2

Despite the interest that Chalmers, and others, have in the Parity Principle, I'm not really sure what help it is.  Here is what A&A, 2001, had to say about the principle:

In defending what we take to be common sense, we don’t propose to challenge a principle articulated by Clark and Chalmers: “If, as we confront some task, a part of the world functions as a process which, were it done in the head, we would have no hesitation in recognizing as part of the cognitive process, then that part of the world is … part of the cognitive (Clark & Chalmers, 1998, p. 2).  To us, this means that the skull does not constitute a theoretically significant boundary for cognitive science. More specifically, it means that being inside the brain cannot be the mark of the cognitive. This seems to us to be true and obvious. (Adams & Aizawa, 2001, p. 46). 

 So, if the principle is nothing but a "veil of metabolic ignorance" (as Clark sometimes describes it)--so that we should not use an in-the-head versus outside-the-head condition as a basis for telling what is, or is not, cognition--that by itself does not seem to me to speak to whether there is, or is not, extended cognition.