The way I see it, the Editors Choice Award is just to show that the editors themselves enjoyed the game a lot. Some games can be objectively great. As in, get 90+% score-wise. Though the editor might still not considerate one of their favorite games.
At least, that's what I'm thinking whenever I give it.
I know the "What's This" part of image says something different, but I think giving something a score of 95-100% shows that it is in some way exceptional.