This might have been a case of parallel invention. When I was using Michigan Terminal System in 1981, and it wasn't new then, I remember SERCOM/MSINK being distinct from SCARDS/SOURCE and SPRINT/SINK. Yes, that's cards as in punch cards. My impression is that similar concepts and terminology have also existed in the IBM world since $forever. I doubt that the MTS folks and the Bell Labs folks were aware of each others' identical inventions, but if there was a relationship I'd bet on the MTS folks having been first.
I'd posit, though without experience of contemporary systems of the era, that the article's more correct title would be 'the birth of standard error in Unix'..
