Evolution Data Vs. Normal Data

[KidProdigyz]

So I noticed if I caught a pokemon, let's use butterfree as an example, it says I obtained the data on it in my pokedex. However, if I level a metapod into a butterfree, it says I obtained the evolution data + the catching data. What's the difference?

 

[Saric]

I assume evolution data goes to where when you do /info on yourself, and it shows how many pokemon you've evolved. Although i could be wrong, but that's the only sensible reason that I see.