Unfortunately, no, he's not joking. It's the case especially with inland clubs based on gravel pits and reservoirs.

The Vortex is described as a tunnel hull, the RYA considers it to be a monohull dinghy rather than a cat. Similarly the Laser Fun (which it most emphatically is NOT) is also described as a tunnel hull dinghy. Before the concept was banned, the International Moth Class boasted a couple of tunnel hull designs and they were very successful.

Of all of these, the Vortex is the closest to being a catamaran. I have sailed one in a force 3-4 and it was an absolute hoot!