It's the last part that I'm not 100% sure of and have trouble visualizing. As I visualize it, if the trout is rising while the fly is coming down, it will never get a view of the fly from directly underneath. The trout has to be near the surface just before taking the fly.
I've seen fish in clear water come from the side and come forward as well to intercept. There's no way they had a direct underneath view.