Is it just another odd piece Game Freak logic? Or something explanatory?
I can understand if it's a really odd stage in in a Slakoth's life.
It's just how it is.
The evolutions don't have to be "logic checked" anyway. Besides, you know GameFreak logic, they haven't got a mind. This leads to major problems, like this.
~ Me lazy, then energetic, then lazy again. xD