He is using the term "concentration camp" in the original sense of the term to mean "prison camp". What we call "Nazi Concentration Camps" were often "death camps" and/or "labor camps", but those are not what he means by "concentration camp".

"Internment Camp" is a euphemism for "concentration camp", which is itself a euphemism for "prison camp". "Concentration camp" has also come to be a euphemism for "extermination camp".

So:

  Is a:                          | Can be called a [...] Camp
  --------------------------------------------------------------------
  Prison camp                    | Internment, Concentration
  Prison camp with labor         | Internment, Concentration, Labor
  Extermination camp             | Concentration, Extermination, Death

He is talking about the first line, you are talking about the third. In modern English, the term "concentration camp" is most strongly associated with the third.

(Actually, IIRC some Japanese prison camps were in fact labor camps, though I think the work they did was almost entirely agricultural. No bomb-assembly to my knowledge.)

@dragonwriter suggests avoiding the terms "concentration" and "internment" entirely and only using "prison" and "extermination" (https://news.ycombinator.com/item?id=6260756). I think this is a reasonable suggestion.