It seems the forcereload of the leaderboard in the GooglePlay plugin is missing? In the GooglePlay SDK you can send String leaderboardId, int span, int leaderboardCollection, int maxResults, boolean forceReload. All of them exist in your plugin, but not the last boolean.
Normally it is fine to use cached data (the boolean is defaulted false if not stated true) if you just want to display a leaderboard for the users, then the data may not have to be totally uptodate, cached data is fine. But if you use the playerscore in the game logic it is crucial that you can assure that the fetched data is totally fresh and not cached (old lower score)
Or am I missing something?