Background

I'm currently developing a simple library that mirrors Game Center's functionalities locally. Basically, this library is a system that manages achievements and leaderboards, and optionally sync it with the Game Center. So, if the game is not GC enabled, the game will still have achievements and leaderboards (stored inside a plist). But of course, the leaderboards will then only contain the local player's scores (which is kind of useless, I know :P).

Problem

Currently I have coded both of the achievements and leaderboards subsystems. The achievements subsystem have already been tested and it works. I'm currently testing the leaderboards subsystem using multiple test user accounts. I loaded the test app on a device and on the simulator, both logged in with 2 different user accounts. Then I performed these steps:

1. I first used the device to upload a score.
2. Then, I ran the simulator, and the score submitted by the user on the device is shown. Which is cool.
3. Then, I used the simulator to upload a score. But on the device, still, only one score is listed.

I checked on the Game Center app (to see if the bug lies within my code), and I got the same thing. Under "All players", there is only one score on the device, but there are 2 scores on the simulator. I wanted to make sure that the simulator is not causing this, so I swapped the users on the device and the simulator, and the result is still the same. In other words, the first user is oblivious of the second user's score, but the second user can see the first user's score.

Then I tried with a third user. The result: the third user can only see the scores of the first user and himself. The second user still sees the scores of the first user and himself. The first user only sees his own score.

Now here comes the weird part. I then make the first user and the second user befriend each other. The result: under "Friends", the first user can see the second user's score, but under "All Players", the first user's score is the only one listed.

Screenshots

The first user sees this:

The second user sees this:

So, is this a normal thing when using sandboxed GC accounts? Is this behavior documented somewhere by Apple?