with 12 frets you usually have little or no fretboard over the body, and some would argue that the top will be free to vibrate more that way. it is also easier for me to fingerpick without the fretboard in the way, if that makes any sense.
Yes, it makes sense. Easier to pick and strum as well. It's why Cuatros and the old ukuleles were both built with flush fretboards.
We're going to do that with our new model longneck concerts. How about those 16 frets to the body with no fretboard at all in your way! For those who want the 17th & up, the longneck tenor goes to 20, but with an extended fretboard. First new concerts head north this week - can't wait!
As far as sound being better, we'll see. I'll be pleasantly surprised if it turns out to be true. There are some luthiers like Rick Turner who go to great lengths to try to get some extra vibes that way. And that's what you have to do - go to great lengths.
Two things hinder vibration above the soundhole. One is the neck joint. To really get somewhere with this approach you need to do some unusual things inside in that regard.
Our neck joint is about as bad as possible that way - we build with the old Spanish foot - the neck structure comes down the inside of the soundboard all the way to the soundhole. Don't think there's much chance that area will vibrate. Just the same, that kind of joint produces such a stable structure that in our experience, it makes up for any dampening above the hole by transfering sound better as a whole (to say nothing of just giving an all around more stable platform).
The other problem I see with that idea is the hole itself. It kills vibration in the upper bout just by being a big hole in the vibrating surface above the bridge. It's why when people try to get something out of the upper area of the soundboard, lots of times you'll see them move the soundhole up into the upper bout.
In short, unless someone has done a lot of reengineering, I don't think having less fretboard overhang by itself will help the sound.