Arrowhead are literally saying that requirement was always there, it was just temporary not enforced/supported. It's not Sony that suddenly introduced that new requirement.
Arrowhead were the ones having this delayed-change-of-contract. Arrowhead allowed their game to be sold in countries where you will not be able to play.
This is the thing that I'm not sure of and that I think the question of whether to blame Arrowhead depends on. Who authorized selling it in non PSN countries in the first place? Is that Arrowhead's responsibility as a studio, or Sony's responsibility as a publisher?
Considering you can find locations to buy the physical game on Playstation's official website, even in unsupported countries, I'm leaning towards the latter