First off, Shane did not experiment with Water skis with alpine bindings first, he just did that for fun afterwards. If you read the Spatula Manual, it comes with a history of how the idea happened and the process by which the skis were finally produced.
Secondly, yes the ARG is a little more progressive than the Spat because of the minimal regular sidecut underfoot, but it was not the first. DP skis Lotus 138 had it over a year ago, so they deserve the credit on that front. Also, I belive the Praxis Pow 185 also has a small amount of sidecut underfoot just like the Lotus and ARG.
Thirdly the shape of these skis has been discussed at length on this site and others and there is a shitload of information out there if people just search.