Flicking a 110 open by holding the blade and doing a drop motion of the frame, isn't what the gravity thing was about.
At one time there were some models that if you worked the blade a little loose and oiled the blade pivot, you could hold the frame and flick the blade open. Some of those supposedly wouldn't hold the blade fully closed in your pocket.
That may be covered better in the links bg42 posted. I didn't go look.
Reminds me of a series of books by Donald Hamilton, whose character Mat Helm describes what sounds like a 110, where he works the blade pivot to the point that he could flick it open. I read those when I was in the service in the mid 60's.
Thus me learning how to grip the blade and flick/drop the frame and open my 110's since my first two dot back in the 70's. Interestingly enough, I have never been cut opening one that way.