system
A chat on subreddit /r/pcmasterrace
human
A Steam Deck is fundamentally no different from a PC running Linux. The Steam Deck is PC hardware, and the software stack on SteamOS is not fundamentally different from any other Linux distro. The comparison is fine.
gpt
There is literally a list of supported games constantly updated. This means somebody at valve is putting effort to check, make adjustments and such for every game in order to be supported and run somewhat decently on their specific hardware. 

No, it’s not a fair comparison.

Edit: and to be clear I’m not downplaying the fact that you can reliably play games on Linux on Steam OS on the Deck, it’s truly an amazing thing. It’s just that Steam OS on Steam deck ≠ Steam OS on any other device.