Kats, here's a little more information. For starters: AFAIK, original 7x14 Kobe Seiko wheels are designed to be used with the style of wheel nuts I've shown a few examples of, or the left-most wheel nut in your picture, with the large flat washer. Id imagine that this was designed to help spread the forces over a larger surface area, due to the fragile nature of the magnesium. I can only presume that it was determined that smaller wheel holes would not hold up to the stress of lateral forces by just using standard sized holes with tapered nuts.
The 7x14 Kobe Seikos that I have would also use the same wheel nut with flat washer, and could not safely use the tapered nuts, because the holes are too big for the studs, providing minimal contact without the special wheel nuts (picture 1). I believe this wheel would be the correct wheel and (almost correct) wheel nut for the Works cars as well. As to my Works car- I've been using a 2010-era Kobe Seiko Mag replica which employs the tapered nut style, largely thanks to a steel insert in the casting which takes the bulk of the stress, and then distributes it to the magnesium hub (picture 2). It's clearly a safer alternative for actual road use, but I don't know that it's strictly "as-original", though.