When there's no player around the lurk won't unburrow anyway if you apply no ai script.
Yes, but if a player comes close enough to attack, then runs away, the lurker will unburrow to follow it, this method would give it to a neutral player as soon as the player got out of range, so it never unburrows.
None.
We can't explain the universe, just describe it; and we don't know whether our theories are true, we just know they're not wrong. >Harald Lesch
Vision is circular, locations are rectangular. If he runs outside attack range in any diagonal direction the lurk would probably still unburrow because the give to neutral would be too slow.
It would definitely not work if he diagonally moves just outside attack range (e.g. tank).