I will explain point #3 in greater detail to make it easily understandable.
Imagine that photons (which include radar waves) are a group of ping pong balls. If you throw a group of ping pong balls against the wall in a long hallway, they'll just bounce down the hallway/cavity.
Now, try throwing a group of ping pong balls into a Mythical Russian radar blocker with micro-ducts, which are roughly the size of the ping pong balls. Most of the ping pong balls will bounce back out. There is your "broad and diffuse specular radar return."
wow !!!
12345678901