Yes. Laptops and desktop machines are included in the desktop platform together. We use the browser useragent to determine the platform and there is not enough information contained in the useragent to distinguish between laptops and desktops. That is why we do not have a separate laptop platform.
So it sounds like they’re using the useragent to distinguish between mobile and desktop. So most likely, yes, steam decks would be counted as desktops, but only to the degree that they are used to browse the internet. I suspect most steam deck users don’t do that, but I don’t know, I don’t have a steam deck.