> I wonder if Valve is still the same as described in this handbook, or if it ever truly was

I recommend looking at companies hiring pages to get a pulse on their longer term direction and strategy (a major reason for bogus job posts btw).

Based on Valve's [0], it's mostly sustaining work for Steam Marketplace, Steamworks, and R&D for VR.

[0] - https://www.valvesoftware.com/en/