The - argument (as any other renderer selectionoptions there is) will only run editor it self on renderer (RHI), it is not needed in development or else is really your main target on desktop, in fact it pointless for mobile devlopment because desktop that will run on editor will not match what you will see on mobile. There Preview mode which you need to enable in experimental to see Vulakn mobile preview which will attempt to simulate mobile conditions as much as it can in desktop environment. It doesnt require - option as editor it self will add that optiion when you will run that preview.