This won't be put in, because it is a chain...
HTC would allow landings anywhere on field
people whine they ditch 2 feet off runway
HTC would allow landings 5 feet off runway
people would whine when they ditch 20 feet off the runway
Chain reaction, eh?
No, it would not have to be. Honestly it is mighty stupid to roll on the grass and get a ditch while you are inside the base

What is ditch?
A forced landing, a belly landing, an emergency landing. Not a perfect landing on grass some feet a way from the runway.
They could put a fence around the base, like there often was in RL. That could be the perimeter and line between landing and ditching. Even then, I would personally call wheels up landings, even inside the base area, ditches.
If the wheels are down and one is inside the perimeter, the only "landed succesfully"
