In the human egg group;
Pokémon in this Egg Group, as the name implies, have similar characteristics to humans. They are fully bipedal, standing and walking on two legs. They also possess arms with which they could manipulate objects or deliver blows. The majority of members of this Egg Group are either of the Psychic or Fighting-type.
If you take a close look at Gardevoir... it's not bipedal. No legs. At least none which we can see. In contrast the Amorphous group (Gardevoir's);
Most Pokémon in this Egg Group are enigmatic in appearance, and the name reflects this. Its many members are based on a variety of things such as gases, blobs, inanimate objects and soft-bodied organisms. Most are capable of floating off the ground. Many of its members are Ghost-type Pokémon
Gardevoir fits this description better as it doesn't really have legs and it kind of floats off the ground. It's probably also soft-bodied to an extent too :P