If Putin were to do this as a KGB type op, which I doubt this is, he would arrange it at Cassino.
There is no benifit to anyone from this. The Russians want to keep their behavior between 1939 and 1940 very very quiet. They don't want the whole world asking inconvinent questions about the meaning of this place. what would have been a quiet time allowing a chance to move on has now become a world wide story. And Katyn Forest brings up all kinds of ghosts that the Russians really badly want to forget.
That Putin may in a small way benefit from this is a remote possiblity. What we will get instead is intense Polish anger and intransigence vis a vis Russia. It doesn't matter that the territory that the Russians stole in 1939 has been inherited by someone else. It was a Russian crime. Hate has a long memory, and this just adds kerosine and Florine to an already too hot fire.