Good question, never occurred to me to ask. I presume its an ICAO requirement applied with out further thought...like that never happens
Further to your question, am I remembering this right, is it not the case that if your wheels are inside the cone markers (as in they define the 'useable' strip dimensions) the rest of the aircraft should be ok?
Like 98% of PNG airstrips if you didn't stay
exactly in the middle of the strip you were potentially in deep doo doo. At Kamalai, as you can see, even in the middle you didn't have much wingtip clearance in a Twotter as you went around the bend...at other strips the area within the cone markers but outside the central strip (often reinforced with crush coral/rocks or some such and about the width of a Twotter/Islander main wheel track) was often too soft and people have come undone. More than 1 206 has ripped the nose wheel out or even flipped when the pilot wasn't careful in this respect. Bush flying, or at least the extreme variety in PNG, is an extremely precise discipline.