Jake,
The"one hulled catamaran" expression was used to point out two important characteristics of this boat configuration. 1. It appears to have a high fineness ratio hull with much righting moment and if built very lightweight, it appears to have potential to reach high speeds like a catamaran.
2, This configuration is very "tippy" unlike a catamaran. It is more like a bicycle in that it must have speed to gain stability and sail on design point. This configuration of sailboat is very difficult to sail at high speeds for more than a short burst. Too many things change too quickly for people to keep them in concert very long.
Bill