The link you referenced just says that the Debian packages are irrelevant to the current codebase, as used on the Steam Deck. It doesn't say anything about the Steam Deck being the only hardware that will ever run it.
Some of the recent SteamOS release notes have included references to Asus's handheld, which has reinforced the community expectation that it will eventually be available as a distribution you can install on 3rd party hardware. If you go read interviews from Valve employees (Lawrence Yang comes to mind), I believe they've publicly stated that after the OLED shipped, they wanted to start focusing on porting to other devices.