Your question intrigued me, so I'm trying 4K on my Mac (hackintosh, RX460 graphics card). I went full-screen, 4K, and noticed two things. First of all, I was limited to 30hz at 4k (possibly a card issue), but then, I noticed that all the text was tiny, and for me, barely legible it was so tiny. Lastly, I'm not sure I saw any advantage over what I normally see in windowed mode.