I'm just reading the summary in the link, not giving Sterling the click. So I may be off base a bit.
I assume Valve, with their libertarian based policies and history of having things stolen from their servers, don't want to deal with the headache of China+Hong Kong politics would bring to their company that Blizz and other PC companies are willing to deal with. Valve makes a bazillion dollars dealing with the rest of the world already, and not bowing to China seems to be one accidental positive of not caring about HK and Chinese based games.