The death camps were not Polish. I can see why they would be upset at the term.
Threatening jail for three years for saying “Polish death camps” is ridiculous, no matter how you slice it.
It seems there are people today who have never heard of the Nazi death camps. Probably Asians or Africans. If they were told about those "Polish death camps" they might think that it is the Polish who were responsible for them. I can't imagine another rationale for that legislation.