That bit about the monitors is some shady crap right there.  1080p looks good on a 4k screen because 4k is exactly 4 times 1080p, so each single pixel in a 1080p image becomes exactly a 2x2 square of pixels when displayed on a 4k monitor, so there's little to no distortion when displaying a 1080p image on a 4k screen.  However, 4k is not an exact multiple of 1440p, it's 2.25x 1440p, so displaying a 1440p image on a 4k panel can result in pixellation, distortion, fuzziness, etc. because you've got extra fractions of a pixel that the scaler either has to discard altogether or stick in places where they shouldn't exist.  The same thing happens with 720p on a 1080p screen.  Years ago when I gamed on consoles I noticed that if you're gaming at 720p it looks noticeably better on a screen if it is native 720p, and worse on a display, even of the same size, if it's a 1080p screen, because 1080p is not an even multiple of 720p.