It makes sense, as it basically boils down to three issues. Firstly, test at max focal length then at min focal length, if both the results are good then it's probably good to go across the range. Secondly, some may select a certain focal length where it's sharpest. Lastly and this is the one I don't like in my case, is that if both ends must be right, then the lens will have to be serviced by the manufacturer to bring the short and long end of the zoom into proper calibration. (Check with the service center to see if this is possible for your specific lens.
Looks like my lens may be off to Nikon
PS. This I didn't know and that is: "You should use an aperture of f8 (stopped down) during the setup and alignment of LensAlign with the camera. The greater DOF allows both the Rear Plate red ring and the Front Focus Plate to both be seen in reasonable focus, which makes aligning them easier and quicker".
Perhaps that's where I've gone wrong as I've been using F2.8!