Sounds like, as always with companies that have huge amounts of employees that deal with the public, that the policies of exchanges, repairs, loaner fees, etc etc etc, have a lot to do with the store and the person you get than anything.
My iMac had the power supply go down, and he gave me the backup of my data for free, when they usually charge $50..his reason for giving it to me for free, "probably didn't need to do it, but it might be wise." Some of the things he backed up, were my wedding pictures, so for my own safety's sake, I would have gladdly paid the $50 for the back up, but he did it for free wirthout even asking.
The fact that they do not allow the techs to "make the decision" on the spot, is simple. Ifyou have every managed a large customer based store, when dealing with complaints, the employee will usually take path of least resisitance. That path would be to just exchange the phone for a new one, as it will get the customer out of the store with no conflict. Sounds good in theory of customer service, but the costs Apple would end up eating for a lot of repairs that HAVE been made for significantly less money than a replacement, would not make that practice wise.
let's also not forget, there are a TON of people that like to try to get one over on the company as well, so investigations by people with the proper abilities of training to make sure the complaints are legitimate product failures is also smart business sense.
Companies do all they can, to make sure that they provide the best customer service possible, while still making sure they are a profitable company. They will NEVER be able to make everyone happy, but as far as most companies go, Apple, IMHO, is handling the tech area of business better than any other tech company I have ever had to deal with.