Accelerometer differences by hemisphere?

Okay, this is a stupid question, I know, but are there any differences between the behavior of the accelerometer in the north or south hemisphere?

The reason I ask: I'm in Australia. I'm making a flight game and it behaves as you would expect. I've tested it on iOS and Android and it's identical.

A tester in the USA can't get pitch control to work right. He's also tested it on both iOS and Android and they're identical (identically wrong.)

I saw in Skype that he is using it in the exact same way I am and even using the same model of iPad.

I have absolutely no idea what could cause this. I suspect it has something to do with the initial position. It takes an initial position, then measures the change from that to get the input. If this is different depending on location, then it might cause that problem, but I'm essentially grasping at straws at the moment.