Wow. I had no idea that existed. That probably explains it - and I'm quite certain if I ever planned on deliberately taking advantage of such it would fail. Now I have something new to research - thanks!
RF is interesting in the path and or paths it may take. You can visually recreate that knife edge effect using a flashlight and a clipboard as the mountain. Hold the clipboard perpendicular to the wall and move the flashlight on one side to see the result on the other.
For me this is a hobby. There is plenty still to learn by experimenting, as each system and geographic location are different. Have fun.