I don’t think it’s a bug, since the wobbuffet is considered an evolved pokemon when there is a wynaut under it, according to the ex compendium:
Q. If I use “Baby Evolution” to evolve Pichu into Pikachu, or Wynaut into Wobbuffet, is the resulting Pokémon. (Pikachu, Wobbuffet, etc.) considered an “Evolved Pokémon.”, or is it still considered as a “Basic Pokémon.”?
A. Any time you evolve a Pokémon. into another stage, it is considered to be an “Evolved Pokémon.”, even if the words written on the card say “Basic”. Alternatively, the quick and dirty way to figure this out is…is there a Pokémon. underneath it? If yes, then it’s evolved. (Jan 22, 2004 PUI Rules Team)