The problem is the idea of trying to define a single source for any river.
Indeed but the issue in this case is that there are certain guidelines that are effectively post the establishment of the first 'source' which then are ignored due to habit and repute. I find it charming that the source of the Thames is often dry.
The other aspect that I find interesting is that given the imporatance of rivers, and amount of mythology that surrounds river sources, I would have expected much more hullaballoo about such claims.