That is it. The padded sail was not for flotation but to give thickness, like the semi- soft sails on faSter ultralights etc. This is a preferable sail profile, but of course has its complications, but when combined with the need for flotation, could justify itself and lead to a technological leap through the back door, so to speak. Wing sails are the future. Spin's are not. When the lift of slotted rigs is realized (very high lift to area ratios off the wind, because the wind can be "bent" around the slats a lot, and drag is not an issue), there will be no need for spin's.
I gues the comparison is that airplanes land at comparitively low speed with all kinds of slots, flaps and slats deployed, because drag does not matter.(you are trying to put the brakes on, and burn up altitude, so you have energy to spare) You need lift at low speed. You could achieve it with a new type parachute foil too perhaps.
A sailboat meets this technology from the other end by not caring about drag when off the wind because the wind (drag)is about in the same direction as he wants to go. He too could (and does) use a parachute/kite type device to this end. They are a pain to deploy, but apparently easier for boats to use than planes....