Does Apple ever have to give you a reason why you're rejected, or tell the truth even if they give you a reason?

That's probably the biggest reason I think that Society (with a capital S) should rein in Apple a bit. They have a lot of power and money over the consumer, but on top of that they have no obligation to provide transparency and truthfulness. Given how dependent people are on their phones, I think it's perfectly fair for the state to step in and say that the power imbalance between consumers and Apple should be equalized a bit.