I think you're seriously missing the point. The point is not "employees for company X are all awesome!", but rather "company X is a good filter". This is no different than saying "a CS degree is a good filter"; it's not the be-all end-all, but it's a nice initial filter.
(Note: I have neither a CS degree (or even a high school diploma) nor have I worked for any of the companies mentioned.)
(Note: I have neither a CS degree (or even a high school diploma) nor have I worked for any of the companies mentioned.)