Well yeah, you shouldn't give much credit to the corporation, but neither should you backlist all applicants who ever worked for them (as OP says some frontier labs do)
I'm not really commenting on that, I just want to remind people that Open Source is highly overrated and should not be looked at as a point in favor of a company.
While I agree with your point I don't agree that open source is overrated. This movement is one of the greatest developments in modern history, and the fact that corporations have exploited it for their own gain should in no way diminish its significance.
Open Source is the company takeover of the good that Free Software represents, I don't really see it as a "movement" by people. It's set up precisely to exploit the people for free labor and look good doing it.