Re-enforcing it after demonstrating it clearly works without makes it look scummy and greedy.
Day 1 policy was that PSN linking was mandatory. Arrowhead execs knew this. Players who bought the game in non-PSN countries should have gotten a pop-up banner saying as much instead of the payment screen.
Sorry to nitpick: They knew people would just work fine without them. But the scare is that now the truth is out in the open and they lost leverage.