I prefer to think of ghost pokemon as pokemon, living born and dying creatures, with some ghost-like features. The original ghosts were part poison and were more like very sneaky gas clouds. Then came wizard-like Misdreavus and gem-eating Sableye etc. The first really spirit/soul-creepy ghost pokemon are Shuppet and Duskull in Gen 3, and it even gets worse in later generations imo. If not Dusknoir is the creepiest thing ever xD
But yeah, there are a lot of strange things in the pokedex entries. If all of it was true, the pokemon world wouldn't really function. So no, I'd like to think it's just stories.