WTH. Maybe I should have searched the globe for a v1.0. My SX600-G v1.1 fan NEVER TURNS OFF. It also sound like a mini chainsaw at low RPM. Or maybe SilverStone is sending the good PSUs to Linus for review. Here's a video I made of my M1's SX600-G with 2 Noctua 120mm rad fans and a DDC 3.2 pump running at low RPM. I even disconnect the pump towards the end. You barely even notice I did anything. The PSU fan sucks and never turns off, at boot, idle, doesn't matter. It just grinds away.
Anyways, I'll be the first to mod it if someone comes up with a solution. We all now know that NoiseBlocker fan replacement won't cut it.