https://www.pcgamer.com/ex-valve-employee-describes-ruthless... This is the most illuminating, but here are others:

https://www.gamasutra.com/view/news/187296/How_Valve_hires_h...

https://www.wired.com/2013/07/wireduk-valve-jeri-ellsworth/

https://www.glassdoor.com/Reviews/Valve-Corporation-Reviews-...

I would take the handbook as more of a vision document than as a true account of the experience.