https://www.pcgamer.com/steam-will-restrict-fake-games-which-exist-solely-for-achievement-farming/

Last year, Valve took action to mitigate the number of trading card farming games on Steam by developing a confidence metric that prevents games from dropping cards until it believes real people are really playing them. Now it's doing the same thing with achievement farming games.

In a brief message posted to the private developer group (which we can read via SteamDB and Reddit), Valve says that these achievement farming games aren't being used by many people, but that they confuse algorithms and users. Because of this, if a game hasn't reached the confidence metric Valve already developed for trading card farming games, it will be limited to 1,000 achievements, and those achievements won't count toward a player's global achievement count or be displayable on their profile. The game also won't count toward the number of games they own, and won't be eligible for coupons.