Thinking about it though, I think I did countersteer in order to drop into bowls while riding vert BMX.
Edit: I should mention in mountain biking you are frequently dealing with a low traction environment, which I think has a large impact on the techniques.
https://en.wikipedia.org/wiki/Countersteering#Countersteerin...
But yeah, hypothetically lower inertia = more ability to steer with weight, obviously.