The hardware is not, but the implications are pretty close (major gaming company is pushing a first party product of open hardware + open software with a linux box). It is literally the year of linux desktop.
This thing is meant for a living room media center. A prebuilt PC with discrete GPU is a much bigger profile (and probably cost). You could say, fine, go buy a small Mini PC. But a system with the current best AMD Strix 890m GPU not only is expensive at $700-1000, but would only have half the performance of the Steam Box if its conjectured performance is similar to an RX 7600.
Dont get me wrong this looks very a nice product, but its nothing revolutionary.