I am a history channel/wings channel junkie, and one thing I have noticd is that many ww2 airbases didn't even HAVE runways. How many times have we all seen the pictures of the spits and hurries taking off, line abreast, across the unpaved field during the battle of Britain? Heck, the original tests of the taildragger me262 were on a grass field!
I guess my point is that landings that end up off the pavement should not be ditches if they are on the airport property. But that's only my opinion. I do think that belly landings should be ditches, on or off the airport, since the a/c would not usually be repairable.