Apparently, this information is based on recent AfD email leaks which are only available to bild.de. As far as I know it is the rule that leaks are launched by sending them to only one press organ, which gives the whistleblower more control about what is published due to relations based on mutual trust. When I am not mistaken no other newspaper will cite the same leakage sources and instead would refer to bild.de.
If the story is true, I assume it was leaked by AfD officials who want to avoid anti-semitism in their party, not least because Gedeon is not the only anti-semite:see Antisemitismus bei Pegida und AfD .
Der Funktionär der NPD-Tarnorganisation "Bürgerinitiative Ausländerstopp" stellte ein anderes Buch aus einem rechtsextremen Verlag vor, in dem die Schuld Deutschlands am Zweiten Weltkrieg relativiert wird. Für jenes Buch steuerte der AfD-Funktionär Stefan Scheil ein Vorwort bei.
Apparently the party needs to find its position regarding anti-semitism.