In an admittedly fast read of the parent article, I don't recall seeing what field the PhD was in. FWIW, in chemistry, there is a very large difference in starting salary, job requirements and career potential between PhD and non-PhD. This is true in academia as well as industry. Non-PhD's tend to be technicians, pairs of hands, or sales. PhD's tend to be researchers and have a far better chance of going into middle management.

Is it relevant? Not sure any more given the loss of jobs to Asia and when the worker crosses 40. But it's been this way for as long as I've been aware.