You got to be kidding. There is so much disinformation in this war it’s difficult to know what the facts are.
Prisoners of war are typically captured in a war zone, that does not constitute holding a prisoner in a war zone.
The Ruskies were transporting them some place, likely out of the war zone. How do we know that they never notified anyone?
And is the Uke communications system so good that if the Ruskies did tell someone, that those manning the antiaircraft weapons knew or even cared about it?
For crying out loud, this is not a gentleman’s game of chess. This is war where things happen, governments lie, military leaders cheat, huge mistakes are made and people actually get killed.
Regardless, POW treatment is specifically covered in detail in the Geneva convention. It is supposed to be followed, on penalty of international and national consequences. The US (and other civilized nations) prosecutes its own defaulters.