They are targeting a different (smaller) member of the same family. Also because my board has to power 5 hi-current DIMM slots while their's doesn't. Moreover, the regulators on my board have special requirements in order to utilize the TurboTrans feature that their linear regulators do not have to meet. Lastly, their board is designed to be sold, so they must be cost conscious in part-selection. My board is for internal use only, so cost is not a factor (thus we can use better, more expensive parts).

Also, this isn't the only reference design I have seen. Here is another one that is very different:

http://www.8052.com/users/hymel/lx200.pdf