I’m actually a bit surprised this takes so long for Valve. Because I think Valve wants to be in a position what they envisioned with Steam Machines, where many systems are created by different manufacturers. Only with a reference model that everybody can fallback to as the base model, the Deck. Guess creating an operating system that can be installed on arbitrary handhelds is not easy (go figure).

BTW this is not a unique concept either, because we had similar strategies before with home computer systems and console like systems in the 80s and 90s: MSX (actually from Microsoft) and 3DO are “popular” examples.