>>3597114999% of the time, egg groups are based largely on the basic stage, hence why Incineroar and the Kalos starters aren't in the Human-Like egg group. The only major exception I can think of (besides Baby Pokémon i.e. Togetic being in the Flying egg group despite Togepi being unable to fly) is the Mareep family being in the Monster egg group which definitely seems more based on Ampharos being somewhat reptilian.
Now look at Ralts. Blobby legs, stubby arms, torso isn't clearly defined. Pretty amorphous if you ask me.
