I just read the account of it on wiki and guess I can see why they had a reason, not that I approve of it, but he certainly wasn't a random jew picked up as soon as he left Auschwitz. I would say that he certainly met the criteria of a spy.
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" Pilecki was ordered by Anders and his intelligence chief, Lieutenant Colonel Stanisław Kijak, to return to Poland (from Italy) and report on the prevailing military and political situation under Soviet occupation. By December 1945 he had arrived in Warsaw and begun organizing an intelligence gathering network.[9][6] As the NIE organization had been disbanded, Pilecki recruited former ZOW and TAP members and continued sending information to the government-in-exile.[6]
To maintain his cover identity, Pilecki lived under various assumed names and changed jobs frequently. He worked as a jewelry salesman, a bottle label painter, and as the night manager of a construction warehouse. However, in July 1946 he was informed that his identity had been uncovered by the Ministry of Public Security. Anders ordered him to leave Poland, but Pilecki was reluctant to comply because he had a family in the country and his wife was unwilling to emigrate with their children, as well as due to a lack of a suitable replacement. In early 1947, his superiors rescinded the order". Continued
We have our Julius and Ethel Rosenberg
Soviets murdered anyone associated with the Armia Krajowa.