A person that died, and lives on a spirit, grudge, whatever, isn’t a pokemon.
The pokemon itself is something different. It is in a sense born, and becomes a member of a species fully capable of reproducing, from the dead possessing an object (Honedge, Sinistea, etc.) or given form (Yamask, Phantump, Froslass, Sandygast, etc.)
That’s as fuzzy as it gets. Being amorphous, levitating, or having cross dimensional abilities doesn’t explicitly mean they’re dead. Those can be just powers, like an Ice pokemon creating snow but not made of ice, or a Grass pokemon not having anything to do with grass.
