We don't know that it isn't Pentile, yet. But my concern is if you take content designed with square pixels and show it on a display with diamond pixels, there will undoubtedly be distortion. Maybe at a high resolution it would be imperceptible, though.
For example, here is a page that discusses the effect of using diamond pixels on DLP projectors. You can clearly see how text is distorted. That is what I meant by the comparison to pentile. This may be something that if used will create distracting artifacts on screen.
http://www.kguttag.com/2012/02/09/ti-dlp-diamond-pixel/