so fonts that fully scale such as truetype … have a min max ratio … they will fill the same number of pixels but as a ratio. The denser the pixel space, the more warped the perspective gets, the blockier the font looks.
Non-scaling fonts that are prerendered at various points sizes have a different version of that problem. They only get so small or so big. And as the applications scale the dynamic background, the fonts start bleeding all over everything.
EDIT: It really has to do with how the font gets rendered before display and if that will translate to the pixel density that the video card and OS rendering system support.