The MacOS built-in screenshot tool has an optional "timed delay" feature, where you can click "screenshot in 5 seconds". With that time, you can open menus, or do anything that requires events to be processed by the application. Very handy for screenshots that require something to be clicked on.
I mean, I can probably do the same in X11 using xwd, with a sleep.
But I just don't want my screenshot button to do anything else than taking a screenshot.