Ok I also try it one last time 🤣
Go to Google images and search for "Desktop". What you see is Desktop machines amd setups and how I and the vast majority of the world use the word "Desktop".
Now search for "handheld game console". It's very likely that one of the first few results is literally a SteamDeck.
Now back to the stats. As I already said. SteamDeck will be tracked as a Desktop because stat tracking sites just use Browser User Agents and try to detect what the device actually is, but that's very hard if not right out impossible because clients (including the SteamDeck) intentionally (for privacy and compatibility reasons) lie about what they are all the time!
If you take your mobile browser and enable "Desktop site" or "Desktop mode" it will lie(!) and make the server think it's a Desktop - even though it is really not. A smartphone doesn't magically become a Desktop PC. If I browse the web with my typical mobile browser - every site will track my activity as smartphone. If I switch to Desktop mode most sites will track me as a Linux Desktop Machine. But my device has not changed.
So you are right that the SteamDeck is tracked as a Desktop PC. But that's because the Server has has either no better category for the device or can't determine what the device really is because it lies about what it is.
https://webaim.org/blog/user-agent-string-history/
Stat tracking always had (and will have) two big issues (which can't really be fixed).
Devices which lie about what they are (see link above) and the problem that they have to come up with some categories and there will always be some devices which fall between the categories (Think fridge, microwaves, sex toys, etc.).
If your SteamDeck is currently actually connected to a monitor a mouse and a keyboard than you are actually using it as a Desktop PC. But if you use it like most people - even though the SteamDeck lies about it - it's not a Desktop, because the word "Desktop" really is about the form factor - it's not just my definition. Give any of your friends a piece of paper and a pencil and ask them to draw a Desktop PC - I would actually be amazed if anybody in the world (even you! outside the context of this discussion) would draw anything even remotely resembling a Steam Deck.
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