The close behavior of popups (tested) and the opened launcher grid for apps should be the same.

A popup (though there is a close button "x") can be closed by tapping in greyed out / undefined / empty areas, I'd expect the same for the launcher grid - which stays and can only be closed by the close button "x" (in top right corner in LTR-languages, I suppose).

The difference can be seen using app sheets -> popups -> ListView Popup (click undefined area -> closes) and launcher grid -> open (click below in undefined area -> does not close)

A difference is of course that the undefined area in popups are basically the whole screen, where in the grid view the home screen widgets "move into the background" and form underneath the known apps the empty/"undefined area", still temperature and volume buttons are defined and are and shall still be clickable.