Ultrasharp is to Dell monitors what "MacBook Pro" is to Apple laptops. Dell clearly intends, with their 24/32 vs cheaper 28, to have pro quality and mainstream quality displays both at UltraHD/4k resolution the same way they have both pro quality 1080p (ultrasharp) and cheap crappy 1080p (not ultrasharp).
It is unfortunate for dell that the 2160p resolution got labeled something so similar to their existing brand.