I don't know titles used by Bell Labs in their old glory days but currently what you say is not correct: They have also distinguished member of technical staff

I don't know titles used by Bell Labs in their old glory days but currently what you say is not correct: They have also distinguished member of technical staff and fellow titles, e.g. see http://www.colloquial.com/carp/mts.html http://www.colloquial.com/carp/mts.html. The titles "member of technical staff" or "member of research staff" used by most corporate labs sound better to PhD ears than "software engineer", I guess, although for some companies they mean (roughly) the same thing.