After seeing the behavior of the 180gr GD it seems that at higher velocities it starts to peel back its jacket and "tuck" the petals behind the core. The jacket doesn't come completely loose and the bullet retains its weight. So we have a case of retained weight, reduced meplat, and in theory increased penetration in the last half of its travel.
In the other hollowpoint tests I have noticed that the bullet does not gain much penetration with increase of velocity, as long as the velocity is within its range of performance. In some cases a lower velocity actually increase the penetration.
The case of 180gr is very interesting as we are able to push it to the point where the jacket is "tucked" behind the core...essentially turning it into a WFN as it's losing its energy. The initial wound cavity does not seem to affected compared to other hollowpoints (actually very impressive!). Without kabooming the gun I think the 180gr GD should benefit from point of "failure" velocities.