I'm not entirely sure about the wooden shell making a difference either. My Hohner in D is obviously made from some kind of soft wood, seeing how easy the screw holes strip out, but the thing is LOUD. Much louder than any other Hohner accordion I have. Although, not as loud as my Doucet with Hohner reeds.
I just wonder how good it is for structural stability. Obviously one can have an accordion made from anything, and it'll stay safe, if the person is careful, but can red pine withstand a lot of wear and tear, like taking apart and putting back together again. Will it ding easier, etc.
Walnut strips pretty easy, I found out the hard way, years ago. Thank God for toothpicks to fix the problem (or at least temporarily, til it all falls out, but that's not a problem if you have more)
Yeah, the sound thing will be debated forever. I personally think it affects the sound, even if it is minor.
As a woodworker, it is probably very stable, and fine structurally, but I don't think there is much question that woods like red pine will not take use and abuse like harder woods. I've started inserting hardwood dowels and strips where screws go when I make one out of a softwood.