In the unity editor playthrough, SteamUserStats.SetAchievement(steamAchId);
returned false.
In a real steam beta test, SteamUserStats.SetAchievement(steamAchId);
seemed to clear. Subsequent calls to SteamUserStats.GetAchievement(steamAchId, out isAchUnlocked)
reveal that it’s true, meaning the achievement has already been unlocked.
I view my personal achievements in Steam and it still says 0/27 unlocked. I restarted steam multiple times.