There appears to be a rare issue where the person accepting the friend request may not see the other user as a friend. Upon accepting a friend request they may appear as a friend but after exiting the game and returning later only the person who sent the friend request may see the other as a friend.

In the same situation it may take an extended amount of time, upwards of 10 minutes before both users see each other as friends.

I have no reproducible steps but the one sided friend issue may be more likely to occur if the user who accepts the friend request exits the game shortly after accepting. May have something to do with the odd delay before both users see each other as a friend when it does not happen immediately.