there's good reason the equivalent shift-command-s isn't bound to screenshot by default... it's the command to save a file and there's no good way to do partial screenshot and full screen screenshot with just command-shift-s + option if you want the option to put it into memory instead of a file. they chose command-shift-3 for full screen screenshot. command shift 4 for partial screenshot and add option to do either of those into memory which is a very common paradigm in macos shortcuts. the option key does something slightly different to the original shortcut in system shortcuts. in any event windows didn't get the non-printscreen version of a screenshot tool until very late in the game and osx had it in for a long time.

that issue isn't even an issue if you really want screenshots to be something else. you can change basically any shortcut in one place in macos. same with kde.