This is true, or an 11-17, 7-speed UG corncob cassette variation. But only on the Dura Ace UG freehubs, not the 600 freehubs.

While I haven't tried, my guess is that by using either 9 or 10-speed HG spacers, an 11-18, 8-speed, could also be assembled on these 126mm spaced hubs.