There are also other factors at play I believe than just resolution. I have 3 XPS 13 laptops - one Full HD matte, one Full HD glossy and one 4K glossy.
Full HD matte seems quite unsharp compared to the Full HD (or 4K) glossy. But with my eyes, I don't really see the difference between Full HD glossy and 4K glossy.
Matte screen by its nature desharpens so it should be expected. But I did not expect the effect to be so noticeable.