So far there are some hints that morpheus might be using optical filtering to reduce screen-door in addition to the RGB sub-pixels. We still have little info about the optics.
The visible screen door is the pixel gap between sub pixels of the same color, not between any sub-pixels. There's also a big gap around all sub-pixels (for the circuitry on glass), so the fill factor looks about 6% on the red channel of a pentile screen. Even if they had an amazing new stacked technology with 100% fill of sub-pixels, the actual perceived pixel gap would average 33%, with only 25% for Red/Blue and 50% for Green.
Pentile is still pentile, no matter what new branding they use, diamond or otherwise. The idea of using a pentile screen for VR is pure stupidity unless your display is significantly higher res than your source. It's a major waste of processing power, as it filters down 2/3 of the data to half the input resolution. The rendering pipeline is not capable of rendering different channels at different resolution. The bandwidth available is also wasted as there are no frame buffers for pentile. It also chains filters which makes the image even worse. Optical filtering is a big clusterfuck with pentile because the optical properties required are different between green and red/blue.
TL;DR
Sony's choice of RGB pixels was an important decision impacting many aspects: processing power efficiency, bandwidth efficiency, screen door reduction, enabling 120Hz, and possibly simplifying (or even enabling) optical filtering if they chose to do so.