Their base stats are all prime numbers, and generally pretty min-maxed. Goes along with the 'not of this world or reality' theme I suppose, plus what can be considered adaptations to their homeworld's climate. A nihilego doesn't need Defense if everything on it's world uses laserbeams and crystals and poison to attack, a Buzzswole doesn't need Special Defense if the landscape is full of huge fucking punch bugs and mountains that also punch and flex, Xurkitree doesn't need much speed or attack but it does need Special Attack since it can plant itself in a larger Xurkitree's root system and conduct assloads of electricity, etc
