There have been a handful of VR-exclusive games now that go beyond basically being a tech demo. Lone Echo and Asgard’s Wrath spring to mind. But they are still vanishingly rare, and the vast majority are still 1-6 hour “experiences”.
Given this is Valve, I will be honestly shocked if this is anything but another gimmicky experience. Rumours that it will be all gravity gun, all the time only lend credence to this, imo. We’ll see soon enough I guess.