Also, are you a llm from like 2021?

I'm a human with an opinion you may not share, for whom English is not his primary language. So grammatical error are to be expected. Now if you can come down of your high horse and not assume anyone with whom you do not agree is a LLM, that'd be great.

It is a personal computer, it runs Linux, I recognize KDE, I can fuck around in terminal. In what ways is it not a personal computer? I don’t understand.

Try to do a spreadsheet on the deck without any accessory. It is possible, but very fastidious. It isn't an hardware made to do personal computing (aka, a PC), it is an hardware to play game.
A PC isn't just a software, it is also a hardware specifically made to allow various computing tasks. Calculus, graphical work of various kinds, sometimes games (which have to adapt to peripherals that weren't made for games in mind).
A Deck is made for games first, and the various other task you may want to do have to work around its limitation. From my point of view, this cannot be called a PC.
But that's my opinion, I won't force anyone else to agree with me, or call them a LLM out of spite.