I think it is telling that the theories as yet have so little currency.
All the narrative seems to be couched in anecdotal terms, with pseudo science explanations after the fact. Some of that may be down to the requirements and exigencies of leftpondian media to create a newsworthy story, but ultimately his ideas have been around long enough (published 2008, 1,000,000! Copies! Sold!) that others would have picked up on it. If it sounds like woo, smells like woo, and looks like woo......
I don't discount the whole thing yet, the idea that you can exercise your brain is not unique to this approach, and the changes brought about may be too subtle to discern, but a tenner for a wobble board and a few minutes of hilarity that will ensue seems to be the right level, but I might just try standing on one leg and save that £10. (One of his concepts is that challenging your brain with a balance problem puts it into a more receptive learning mode)