A 91 ppi pixel is nothing like a 300 ppi pixel, so this "pedantic" definition matters. Particularly as retina-like displays become more and more common.
And whether they are doing it to the same accuracy as this article recommends or not, browsers are not simply rendering 1px as one pixel width regardless of the display resolution - My 2 year old iPad with a retina display demonstrates this well.
And whether they are doing it to the same accuracy as this article recommends or not, browsers are not simply rendering 1px as one pixel width regardless of the display resolution - My 2 year old iPad with a retina display demonstrates this well.