Part of the argument is that a monohull doesn't need the elaborate structural engineering that a multi does to keep the mast in place. Some of the weight saved can go into a lead bulb that they claim to have designed so it can be canted to windward -- out of the water.
The other thing, as we've seen with Open 60s, is that these boats will always be reaching so they will always be heeling. When heeled, the immersed hull is very skinny -- like the leeward hull of a catamaran. The shape of this hull is not unlike something I sketched for Mike Plant at his request back in about 1990 (tho considerably longer . . .).
It does appear to be a stretch, but I wouldn't totally discount Vlad Murnikov (if he can raise the $$$).