There must be a typo in the article you linked to. The German Wikipedia says that in 1965 copyright in Germany was
extended from 50 to 70 years.
https://de.wikipedia.org/wiki/Geschi...0._Jahrhundert
That extension must have been what Schmidt referred to in the interview, so what I got wrong were the copyright terms pre- and post-extension. What I clearly remember is Schmidt saying that 20 years was plenty.