On Samsung this sometimes happens when the app hasn't been closed since the resolution change. Once the app is closed and opened again the text size returns to normalThere is a noticeable difference on the OnePlus 7T Pro. I'm not sure if it's their implementation or what. Now there's absolutely no difference in sharpness I agree however when I set my 7t Pro to FHD the font sizes all go up a notch. I tend to run with the smallest font available so I can fit as much as possible on the screen. So that's one drawback in changing resolution.