Sunfish,
No idea about YMMB, but I think Fieldmouse is probably correct about the airport being resurveyed for obstacles. Sometimes it could just be that some trees have grown up within the runway splays.
As for the practice of landing short, I think it is a habit that should be avoided. It might seem safe at YMMB but there are airports where the obstacle on short final can be a real threat to life, and quite often unseen. i.e. powerlines.
Fly safe.
Clark y.