And if it did not report it, it was because in all probability a massive extermination of Jews never took place. This, therefore, is the only satisfactory explanation for the silence of the Polish Fortnightly Review.
Auschwitz and the Exile Government of Poland According to the ‘Polish Fortnightly Review‘ 1940-1945
Another especially well-informed courier was Jan Nowak (Zdzislaw Jezioranski). Nowak was selected in 1943 to travel secretly to England, carrying the maximum possible information. With this in view, Nowak met that summer with the head of the Biuro Informacji i Propagandy (BIP – Bureau of Information and Propaganda) of the AK. The chief of the BIP was “in a sense minister of AK internal propaganda and policy. He controlled not only the military underground press, but also a widespread information network.”  On order of this person, Nowak met also with the section heads of the BIP, among them the head of the “Jewish section,” with all of whom he held “long and exhaustive” conversations over a period of one month.  In consequence, when he set off for London in the summer of 1943, Nowak had to be one of the persons best informed about what was going on in Poland.
Nowak arrived in London in December of 1943. Some months later, in mid-1944, he was ordered to return to Poland, where he arrived via parachute. He took part in the Warsaw uprising; after that was crushed, he managed to escape to London in January of 1945.
In short, if there had been a massive extermination of Jews in Auschwitz, the leadership of the resistance within Poland would not have failed to communicate it to their superiors in London, either by means of radio messages or by courier. Specifically, couriers such as Jan Karski and Jan Nowak men specially trained to carry the maximum possible information to London would certainly have communicated this terrible occurrence to the Polish authorities in exile.