>Sylveon, Umbreon and Espeon evolve with human friendship
>Jolteon, Vaporeon, Flareon, Leafeon and Glaceon can plausibly exist in nature, as their methods of evolution are rocks and stones found in the natural environment
>Umbreon, Espeon and Sylveon have some form of way to make up for the lack of opposable thumbs(Psychic powers for telekinetic abilities in the case of Umbreon and Espeon, fleshy feelers in the case of Sylveon), but the other five do not.

Umbreon, Espeon and Sylveon are not adapted to nature, but to human lifestyle, and have developed some form of way to supplement the absence of the opposable thumbs that humans possess, so that they can live like humans.