[wfn]

It might be that the experiences/conditions were a bit different: perhaps (shameless utter speculation) Viktor Frankl had in mind those cases in which people were not intentionally murdered, but rather died themselves (starvation / reluctance to eat / falling apart / suicide). e.g. (wiki):

"On 25 September 1942, Frankl, his wife and his parents were deported to the Nazi Theresienstadt Ghetto. There Frankl worked as a general practitioner in a clinic. When his skills in psychiatry were noticed, he was assigned to the psychiatric care ward in block B IV, establishing a camp service of "psychohygiene" or mental health care. He organized a unit to help newcomers to the camp overcome shock and grief. Later he set up a suicide watch, assisted by Regina Jonas."

Then again, e.g. his mother was killed intentionally in gas chambers. etc.