Let's be honest there was never a fucking theme or pattern ofr the starters
Zodiac was the closest one and even then you had to stretch for it

>Grass muh prehistoric theory
Chespin is a chipmunk, Rowlet was is an owl, and Grookey is a primate, none of those are prehistoric, and no, an obscure reference to giant owls doesn't mean shit

>Water, muh amphibious animal
That's not a pattern, that's just GF basing shit on popular animals you tend to think go with water.