SysCfg with serial number etc has been on a separate NOR chip for quite some time [1]. I wouldn't be surprised if Apple allowed DFU restore to initialize a blank flash as mere optimization in the production process.
Your link only lists NOR sizes for the original iPhone and the iPhone 3G and then goes on to say "iPod touch (3rd generation) and beyond -- The NOR is replaced with a dedicated partition of NAND"