But how many billion-dollar companies would do that? Just give the rights to the ex-employees? I think most other companies would have not. So, in that sense, Valve is unusual, even if it's not the oranizational utopia that was promised.
After she left Valve, she and partners did get at least $15 million funding from outside investors to develop the AR technology, but after several years of trying, it didn't work out. https://en.wikipedia.org/wiki/CastAR
I'm not sure why Steam always seems to be exempt from the "perils of digital ownership" arguments