People have been doing it for years as far as I know. It’s kinda where this whole “review bombing” thing comes from. It seems like Valve’s policy is to label these kinds of mass reviews as “off-topic activity” and remove them from affecting the normal rating for the game. If you see a game with an asterisk next to its score on Steam, hovering over the asterisk will tell you that some reviews have been removed from the score for this reason. They’re still publicly there, and you can go into the details of the score to see those periods highlighted, but they no longer affect the score that you see on the storefront.