Nope, I had touched down, I was on the ground and rolling out with the autobrakes decelerating the plane. I tapped the brakes and chaos ensued.
I think this was the result of mathematical calculation bug resulting in unrealistic asymmetric force vectors - note the crazy bends of the wings as the aircraft spun around. The net forces also exceeded the force of gravity and the weight of the aircraft, which is why it was literally tumbling vertically upwards, lol. It must have been some glitch involving ground friction, lift, and drag.
I really wish I had video of this - it was bizarre.