By definition, a gancho can't happen without that interrupting leg, for one thing.
It's actually happened to me, in the last week! I was leading an overturned back cross step to my right, and intended to lead a gancho, but never got to intrude my leg in time (because we were both hopelessly off balance, but that's another story). She obviously thought I intended a gancho (I did intend one), and she duly flicked her foot back - but there was nothing there, until she came back down again, by which time my foot had arrived, and I got kicked for my trouble.
It was very funny, but it underlines the paradox, for me. She 'should have' just taken a back step - but she was never going to, and it wasn't making contact with my leg that made her suddenly be 'active' in shaping a hook, because it wasn't there.