I think the short coupling is an optical illusion. The biplane has a second wing and sometimes looks "fatter." Case in point: The Gee Bee R1/R2 series. They have about the same moment as the 'Y' but for some reason everybody calls the R1/R2 series a flying deathtrap on the ground and the 'Y' a *****cat. Go figure.

Can biplanes be difficult to keep orientation on? Sure, however I don't think they're any worse than many monoplanes. I do admit that I've only flown biplanes a couple of times, so take this post with as much salt as you wish.