I think the problem is that "tempo" is a bit of a nebulous term. I think people treat "tempo" as if it were one pace when it is not. Tempo, at least as I have always understood it, refers to a range of paces.
What you are describing above is the classic rule-of-thumb for lactate threshold (LT) pace. LT pace is clearly very specific. But that's pretty much the high-end of tempo. On the flipside, while tempo may be as fast as LT pace, it may also be slower. Longer tempo runs, done at slower than LT pace, are a staple of great runners. Even a marathon paced run is arguably a tempo.