Many answers to many questions. Yes, digital is partly to blame for the sheen, which does not bother me! Yes, the grains orient themselves in the direction of flow which is through the hopper, and thus they are parallel and flat!
Jim, yes, there is a deveopability differential from top to bottom. Part of this is controlled by the Iodide and Bromide in the emulsion and part from both of these in the developer. That is why I have been so vocal in complaining about home brew C41 developers. If you get it wrong, you suffer consequences. There are several restrainers in each layer plus the DIR couplers which adjust development rate. The complete formula for Portra film is given in a patent, but OTOMH, I cannot remember the number nor the inventors. As one who worked on Gold 400, I can assure you that this question is not trivial and is at the forefront of our minds. You use ballasted restrainers and accelerants to achieve a proper rate so that all layers end up at the right point at the right time. This is why I avoid push or pull process. I over or under expose instead.
This question also is the reason why I complain when someone says they can do C41 at 20C or some such. It just does not work right. BTDT!
Maybe I should write Volume 2 of my book and include a complete workup of a color system!