Steam continues to tinker with how user reviews affect a game's overall score on the marketplace. Now, reviews from those who received the game for free do not count toward a game's overall user score.
This change includes those who received a game as a gift, or during a free weekend. Back in the fall, Steam changed its review structure to scrub reviews from those who bought or acquired activation keys for the game (as opposed to acquiring it from Steam). That was explained as a preventive measure against what Steam viewed as gaming its reviews system.
Steam at the time identified more than 150 games for which user reviews from Steam keys were demonstrably more positive than direct purchases. An analysis later done by Steam Spy found 427 games most affected by the change, with the implication being that developers of the game had sent Steam keys to influencers or others who were inclined to praise it.
The latest change effectively means that only a direct purchase from Steam is going to count to its overall user score. It doesn't cover free or free-to-play games, obviously. In all cases, reviews may still be written, and they will be available for users to browse and read, they just don't factor into the overall number.
Steam started rolling out the change earlier this week, but it will take a few more days to recalculate all of the user scores in Steam's catalog. This means a game's score may fluctuate until the update is complete.