Have you actually compared the same content on a 200 PPI screen vs. a 300 PPI screen? Even though you cannot see the individual pixels, text on a 300 PPI scree

Have you actually compared the same content on a 200 PPI screen vs. a 300 PPI screen? Even though you cannot see the individual pixels, text on a 300 PPI screen appears much sharper (when scaled to be the same physical size, of course). The "visual threshold" doesn't mean "you will not see anything smaller than this so it cannot physically matter". You can still see a hairline even if it's less than 1/300 inch wide.