Oh you can't blame them for not knowing the exact number of Pokemon. Even to this day, the numbers will keep on increasing until the creators run out of ideas. Oh how I miss the movies back then. They were as awesome as their theme songs. Haha sorry going off topic. They stated 150 since the audience weren't going to be satisfied without being given an exact number. If Professor Oak said to use the Pokedex to find over 1000 Pokemon and Ash couldn't find that many, you expect everyone to be angry. Nothing's perfect even movie and anime story lines are flawed unless you want them to remake them but that would ruin its classicness.