[Bug-gnubg] crashed position

[Mark Higgins]

I'm trying to find the exact definition gnubg uses for a "crashed" position.

The one reference I've found (Thomas Haug's thesis) says it's contact, plus the restrictions that the player has fewer than 7 pieces remaining with none in the opponent's 1 or 2 position. Is that correct? 

If so, can someone give a little color on why those particular restrictions? eg why is it contact if the player has a piece on the opponent's 2 position, but crashed if it's on their 3 position?