Except Apple is paying the arbitrator, so they are inclined to give them the benefit of any doubt. Not saying you can't win in arb, but it's an uphill battle.
Apple is paying the arbitrator because it's a requirement of arbitration.
Apple is happy to do this because even when the arbitrator decides they're in the wrong it'll 1) be much faster than court 2) be much less than a jury awards. There are pretty much 2 arbitrators in the US and so they can afford to lose a single client.
Its only uphill if you have an actually bad argument such as _just_ the statement "they broke our TOS.".