Yes the mast rotates.  Having the rotating arm at the masthead, however, means that the mast will only rotate as much as the sail does.  That significantly limits the performance advantage of the rotating mast.  Standard practice, when sailing to windward, is to rotate the mast more than the sail, which creates a smooth entry to the leeward edge of the foil, eliminating turbulence at the luff.  This adds notable speed to a high-performance racing boat, though I wouldn't choose it for cruising.  I'd choose a hull/rig configuration like Marie G, perhaps with a lifting keel, depending on location.

There is something I don't understand about that rig: the normal practice with wing masts is to over rotate them, to get a smooth lee side.  However, that gallows at the top is fixed to the mast and seems to prevent over rotation.  At that point, you lose much of the benefit of rotation.

Aerodynamically, this would make more sense to me with a sail that wraps around the mast.

I followed the link and found the sail to look very promising (but lacking in detail about battens and camber), so spontaneously I registered and wrote a comment on that site.

The fact that Parker hasn't sold a single sail plan could mean that it is not good, but it is not a proof that it is bad. I guess it took 15 years before the numbers of copies of the cambered panel JR from Stavanger reach ten.

BTW, Ketil Greve In Marie G won a single-handed race in Bergen this week-end. I am looking forward to reading his story here, when he returns.

Arne

PS: OK, I see now that Parker has some sort of hybrid battens , being bendy in the fore end and straight in the aft end. Maybe that could work, Only practical testing would show what is best...