It just says that the max resolution of WP7 was so low that it was possible to cram 3 subpixels/px. Or if you see it the other way around, with such a low ppi the only thing they could do to mitigate the loss of quality was to go RGB. Now for the 920 they went LCD which is an entirely different ballpark. Btw clairvoyant is a samsung subsidiary if i'm not mistaken. It's simple. You can't go well over 200ppi with RGB amoled.
So the initial question should be, why do manufacturers still use LCD?