That is interesting . . . so the block rotation was arrested by the resistance of the intact building below, but the same resistance isn't sufficient to slow the collapse beyond 10% of a free fall rate in a vaccuum . . .
That's correct (assuming 10% is notional, there's a few estimate of the actual ratio), because the rotation is not being driven by gravity at that point, as the upwards resistance is evenly distributed.
So the resistance needed to stop the rotation is similar in scale to the resistance need to stop the building moving slowing in the absence of gravity.
It's like the difference between pushing a car on a flat road and lifting the car off the ground.