Is there any reason why your tests don't include a single "knock-off" Chinese carbon stem?
I'm guessing it's because fair wheel bikes doesn't stock or sell them? FWB is a store not Tour magazine. They really don't have any obligation to test every single item on the planet, especially if it encourages you to purchase a product from another vendor.
Having said that, I am disappointed there's no testing of Ritchey wcs 4 axis alloy version to see if the god awful faceplate design of the c260 has any merit on actually improving stiffness.