Think about the mechanics of the M14/M1A scope mounting system for a moment.
The inner, mounting surface of the typical mount mates up to the side of the receiver and is secured by the big screw. The second screw on "Generation 3" mounts fits into a clip guide block. If the two screws, when tightened, put *any* bending moment on the mount, the threaded fasteners are no longer in shear only but in tension also--not a good thing if you want them to stay tight as you bang on the mount (by shooting the rifle).
The Fulton Armory Mount allows for this "misalignment" by providing lateral adjustment of the clip guide block mount during installation. Properly installed, the screws are in shear only, with no bending moment on the mount, as good practice demands if the screws are to remain tight. It cams into the alignment groove on the receiver, ensuring 100% lockup in the groove.
If, when installed, your mount fits your receiver grooves well, and your clip guide mounting block is fortuitously positioned so that there is no bending moment on the mount, you are likely to enjoy satisfaction. Often these conditions do not obtain; thus the Fulton ARmory mount is designed to compensate for them.
Note that the clip guide was never intended to be part of a scope mounting system, so the location of the roll pin hole with respect to the left receiver wall is not held to any particular tolerance. Heck, the grooves in the receiver aren't held to a tight tolerance, either! The weaknesses of the original single-screw design only became evident in service; that's why the two-screw design was developed. Fulton Armory has simply gone the next step. Call it a "Fourth Generation" mount!
Hope this helps.