the view details buttons that display a very blurry scaled down version of a screenshot is imho quite useless. to me details would provide actual details such as if the theme supports keyboard layout change, virtual keyboard, etc.
the sddm greeter cli command is better in that sense, but one has to go a web search or go to arch wiki to learn it exists and it is a waste of time to have to switch from system settings to a terminal to type a command then kill the preview window switch back to system settings to be able to change the theme. it would be more straight forward to expose this feature right from the GUI imho.