It's simple, really: The Pokedex is bullshit.
The Pokedex reads exactly like a Pokemon wiki maintained exclusively by small children, which is appropriate, because that's what it is. It claims Wailord weighs something ludicrous like 10kg and that there's a Pokemon who's literally God and some Pokemon will steal your soul or whatever. It might as well claim that the Phil Collins song In The Air Tonight is about the time a Gulpin watched a woman drown, or that if you say "Slowpoke" into a mirror five times, a Slowpoke will move into your home and hog all the blankets.