It's a thing if people say it's a thing. It's just a made-up term which tries to equate Durham with Oxford and Cambridge. If you believe that, then it's a valid term. If you don't, then it's nonsense.
I've never heard the term before this thead but apparently it was coined over fifteen years ago. Doesn't sound like it's been given much creedence - less than 6000 hits when I Google it. Not much for over a decade and a half of existence. All in all, it sounds like an embarrassing Epic Fail by Durham's PR department.