Kraftwerk started being called "Techno-pop" around 1978 by a Japanese critic, and the term caught on in Europe. "Techno" alone was a term being thrown around in 1982, perhaps earlier, by German press (and even Billboard seems to have used it) to talk about electronic music in general, from Kraftwerk to New Order to Front-242.
However: those European acts that were called "Techno" in the early 80s are now retroactively called "Electro" or "Synth Pop".
Interestingly, the early-80s Bellevue Three music, by the way, is much closer to the "Electro" camp, as the popular tunes often lacks the four-to-the-floor associated with today's techno (which the article itself talks about), and feature a breakbeat instead (check out Afrikaa Bambaata for comparison).
The four-on-the-floor itself was already a feature on electronic club music like Trans Europe Express by Kraftwerk and I Feel Love by Donna Summer, both 1977. Italo Disco (early 80s) also mainly featured that drum beat.
The term "Detroit Techno" and the style itself, featuring the four-on-the-floor, only appeared in the late 1980s. Some people say 1987/1988.
And to make matters more complicated: by the time Detroit Techno was flourishing, there was already some music from the Frankfurt Tape Scene that was starting to sound like modern Techno (EDIT: some examples: https://www.youtube.com/watch?v=wT_K28uMxNY). It wasn't something that happened overnight, in Europe it mostly evolved from Acid House (which also used the four-to-the-floor as a rule), while in Detroit it evolved from Electro.
To me, the confusion happens because of some disagreements about terminology. First, groups that Europeans called "Techno" are now being called "Synth Pop" or "Electro" because they sound different from modern dancefloor Techno, or because they made more diverse music (Bigod 20 and Nitzer Ebb are called EBM). Second, the misconception that early-80s Detroit music was "the real Techno", when in reality it wasn't exactly modern techno, it was closer to Kraftwerk and Afrika Bambaata.
In reality there was a lot of music being called Techno and a very rich heritage, but some people want to say theirs was "the real first", while in reality it's not that simple.