That line about update arch base means it is shipping only a year old packages and not 1.5 year old ones.
So, depending where you look, more current than $FAVORITE_LTS... with a distribution found on mass-market gaming devices intended for precisely three wrappers. Why do you, presumably a normal user, even care about the packages? Eesh.
As long as Valve provides more snapshot updates in the next six months, I don't see the problem. The ~~TiVo~~ toy is maintaining currency.
I'll concede this might be annoying for the subset that chooses to use a Steam Machine as a server or development workspace, once the product releases. My condolences to this imaginary and small group. They'll be shocked to find immutability, too.
When you maintain systems long enough you realize that's a feature rather than a bug