Pokémon Documentary: Slowbro | Pokémon lover

Pokémon evolution is usually one-way, but Slowbro is different. Slowbro only evolves because a Shellder bites its tail. As long as the bite remains, Slowpoke becomes stronger and more intelligent. But here's something that's rarely discussed: If the Shellder releases its bite, Slowbro doesn't die; it reverts to Slowpoke. This means this isn't a permanent evolution, but a conditional one. So the question is, is Slowbro really a new Pokémon? Or is it just a Slowpoke whose power is being borrowed?