>>15771774Because the real forms of those fossil Pokémon will forever be unknown to us and we have never seen them. Instead we get the part-fossil versions that have been reanimated and have the Rock type forced onto them as part of the reanimation process.
Unless, of course, all Pokémon genuinely were Rock type back in the day, which is a possibility what with Relicanth and all.
That said, if there was a meteor/a legendary meteor Pokémon struck the planet and wiped out all dino-Poke life in one shot, Rock type or not, I don't think any amount of Dittos would be able to breed with them at that point.
