Not true. I bought an AT&T model "device only" for the full price yesterday and didn't need to provide any information. It is fully unlocked (I got the "congratulations" message when I plugged it into iTunes to copy my music library).
It isn't the "official" unlocked phone, but as long as you buy it "Device Only" from Apple it will be locked. Actually, at least for now all Verizon models are also unlocked, even those bought on contract.
That's great but where did you buy it then ? I'm from France and I tried to buy the iPhone 5 16Go on the ATT website and I can't. Did you just buy in a store or online ?