US iPhone 3G Only Designed for AT&T?

Let's first read a report from Aksam

Let's have a look at a details not mentioned yet. When looking at the specification for the US iPhone 3G (here), on can read "UMTS/HSDPA (850, 1900, 2100 MHz)".
If one look further at the specification of the 3G network in USA, one will immediately notice that only AT&T 3G network will be compatible with the iPhone 3G. According to technical specification of the US competitors, their 3G network will simply not work, making any unlocking of an AT&T iPhone 3G for being used with another carrier almost useless.
Indeed T-Mobile is the second largest US carrier with its own 3G network but based on a different bandwidth (1700/2100Mhz) instead of AT&T (850/1900Mhz), as indicated in T-Mobile wiki (http://fr.wikipedia.org/wiki/T-Mobile_USA). So indirectly Apple might have found a way to maintain AT&T exclusivity in USA, in Europe the 3G network is the 2100 MHz bandwidth.

The specification of the iPhone 3G has been designed to fit with the largest number of carriers worldwide, and especially for countries were such networks are massively developed.