Yes, each starter creature is "final" if you will, their stats will vary, for instance lower spectrum HP (green rarity), higher spectrum ATTACK (epic-legendary-holo rarity) and the same for AGILITY and DEFENSE, the average of those rarities then determines "the creatures" rarity. Then as you level the creature up through battles against wild creatures - they'll be at lvl 1 from the vials - they will gain a spectrum of stat upgrades based on how "difficult" the fights were. More on that in another post!
I'll finish this series going through the vial stuff first, then move onto the gameplay and professions more, this'll then also allow me to update the whitepaper as a lot of stuff has changed/evolved and set up a FAQ for the website!
This does not include their "evolutions" however, those are extra and will boost a creatures stats mainly without affecting rarities.