That's ridiculous; are you just making an argument for the sake of an argument, or have you never actually used a phone? Surely it is known that phone operating systems (unlike Windows) don't render anything based on number of pixels, but only on physical dimensions. Thus, on a high-res phone, all elements will be exactly the same size, just sharper.
But, hey, your argument "read text documents" barely even holds in the desktop world either, considering that every single PDF viewer and every single document editor (like Word) render text in a resolution-independent way, and that every browser and almost every respectable pure text editor have built-in scaling features to increase text size to anything you want.
Really the only thing that falls behind in Windows at least is rendering of UI elements and OS menus/utilities.