I think I like their previous design attempt better than these blocks. Am I correct that in the photo with your hand that the circle under the weatherstripping to the right is for tightening down the block? Doesn't look as seamless as their extruded rail you showed previously.
Also, in that same photo, that doesn't look anywhere near watertight around the tailgate. The rear gasket doesn't seem to even touch the tailgate and it looks like water would easily get between the tailgate and the bed on the sides, right?