I understand your point Mad... I was able to mount a Thule Fork Mount directly to the factory rack with some parts I stole from an older gutter mount. It just wasn't a great solution. The 889XT is fine. It is sort of a 'rack to a rack' solution but I think if you saw how it looked it wouldn't bother you at all. It's a clean and stable solution. I ain't puttin' up Sears 10 speeds so the stability and reliability is incredibly important.
Also, if you notice the MDX factory rack is bowed. If you mount directly to it, your bikes will always be leaning. With the Thule 889xt the Thule Bar balances that out. I would post some pictures if I could...