I am going to reply to my own question here.

I just talked to Ben Hall of Hall Spars. He makes masts for a living, so I asked him what a wing mast is. He said there is no real definition anywhere, but he would consider any of the conventional, air-foil-shaped, rotating masts that are on most modern catamarans to be wing masts. As far as he is concerned there is no particular chord length and no magical ratio between chord and mast thickness that determines what a wing mast is.

He said an A-Class mast is about 5 3/4 inches by 2 1/4 inches, which is not substantially different than the masts on Hobies, Nacras, etc.

He said the deeper the chord of the mast, the less practical it is for small cats, and a full, solid wing mast (wingsail) is totally impractical, because:

#1 They are very fragile and usually get wrecked if the boat capsizes.
#2 You have to take them down every time you are on shore, because the boat can blow over so easily.
#3 You need a team of three or four people to raise and take down the mast, because of its fragility.
#4 You need some sort of box ("violin case" was the term he used) to cover and protect the mast because if somebody just trips over it while walking past, it can damage the fragile surface of the mast.

"The full wing mast is esoteric and beautiful," Hall said, "and I would love to have one on my A-cat, but it is just not practical."