* We know that the real one was trapped in the mysts with no way out.
* The whole area leading to him was stacked with mesmer traps upon mesmer traps, while Palawa speciality is necromancy
* As far as we know, the whole "destruction of dragons will lead to destruction of Tyria" is a very sensitive information probably only disclosed to a very tight group of people. Palawa Joko is not on the list.
The public want to know.
I mean under Caudecus and the time of free press, the government would never have gotten away for hiding such important data to the public.