If you click on the link I provided, the catalogue says it was double-butted and that was what I was relying on. It also says that the frame weight is the same as the Muni Mula, but you'd expect it to be slightly heavier if it wasn't double-butted. Maybe the catalogue is wrong?
More likely my memory is wrong, but there are a few differences between the catalogue and the tech manual - the tech manual also has a bit more information.
It also wouldn't be the first time a manufacturer claimed a plain gauge bike was double butted.