Ratings

I guess it depends how powerful they are. It can either be good in defense or attack, but then they didn't say much on the rating scale.

GamePress seems to do an analysis of each Pokémon's strengths (base stats, cp, moves) and potential weakness (typing, gym meta) and applies this to their overall versatility as an attacker and defender. Their final rating seems to be an average between how they'll perform at both

They use rng. Simply rng, multiplied by 10, rounded by 0.5

They give pilo-"dragonslayer"-swine a rating below magmar. They give machamp a rating below sandslash. There cannot be any sense or logic behind it, only a pure rng can explain this.

I could give a better rating with a reasonable scale by defining criteria first and then use these criteria to do evaluation, and a little bit of common sense for fine tuning. I could do this within one week, and i am sure, it would be more relevant than these rng-numbers.
Sorry gamepress, this is weak.