They weren't "prisoners of war"...the war was already over when they were "recruited" at gun-point. They were also civilians, which makes it impossible to call them POW's unless you are also willing to admit that Russia committed war crimes just by capturing them..
And even if they were active combatants...once the war is over, you're supposed to let them go...unless they are charged with crimes committed in the act of service. Then they are expected to stand trial for those crimes, where evidence is presented to prove their guilt. That is typically reserved for high ranking officers, or political leaders.
None of that applied to Operation Osoaviakhim. What you are conveniently reframing, is called politically motivated "slave labor"...something the Soviet Union did to even their own citizens, if they refused to cooperate with the State. These people were scientists. None of them committed war crimes. If they had, then they should have stood trial with the rest of them at Nuremberg. But all this happened after those trials were over.