I disagree. I have a free web game with ~22 rates and 1 one-star review. How could people be verified owners for a free web game with no downloadable files? Also, this would just lower the amount of rates and reviews given. I have also seen the opposite happen for my game. I saw someone who gave me a 5 star review with a account just minutes old at the time.
Viewing post in The rating system and voting bombing...
If I remember correctly, GOG shows you two values: one general and another for people who have purchased the game. It would work as a filter if the game is indeed paid; if the game is free, it will only show you the overall rating.
Personally, rather than a system like that, I think it would be better if Itch publicly displayed the comments on the ratings. That way, users could determine whether a rating is relevant or not.