It seems you are doing research on Creo/Simulate behaviour.... I doubt anyone has looked into this more closely than you have.
A few remarks:
* You have fully constrained the sides of the bottom plate. This may be why you do not get a nice even pressure distribution, because the sides of the bottom plate are now infinitely stiff
* Your top plate appears to be hanging over the edge, which would mean large displacements... not sure that is right?
* All movement in first step: that kind of makes sense because you will have micro-movements due to elastic deformations. Once that is settled, I can imagine there is no more relative movement b/c the tangential force cannot overcome friction. (I could even imagine that Creo first calculates elastic deformations and then contact in the next phase of the calculation, but that is pure speculation from my side).