Evolution randomizes stats?

According to the guide on this very website...
https://pokemongo.gamepress.gg/evolution-guide

The Pokémon's stats, weight, height and moves are randomised. The options are selected from a list that is dependent of the kind of Pokémon;

...and...

Lastly, the randomisation factor means that every time you evolve a Pokémon to it's final form, you roll these stats for the perfect combination to suit your team. Sometimes you will have to evolve quite a lot to get your moves just right.

...Huh? What does this mean? What stats are being changed? Is it the IVs? I tested by evolving a couple Shupets and they both got the same appraisal after evolution as they did before.