Question Why does my GPU keep spinning even when PC is off?

[nenenmahicon]

My PC:
Ryzen 5 3600
Asrock B450M Steel Legend
AMD Radeon RX 570
Seasonic PX650

Question:
I recently swapped my corsair power supply to a modular seasonic one. I connected everything and it worked okay. The weird thing is that when i shut down my PC, the GPU fans started spinning. I know that GPU fans spin on startup or when it hits a certain temperature. But i don't think that it should spin when the PC is shut down. I tried swapping the modular cable to different slots in the power supply and it still happens. The fans spin even when I switch off the PSU. I also tried to remove the power cable of the power supply and it still spins (perhaps due to the capacitors). Its only when i turn on the PC that the fans spin really fast then stops (This I think is normal). It has no noticeable effect on the performance of my PC but it just bothers me especially that it might be consuming unnecessary power from the grid. Was it a mistake on my part or is it something I do not know about the power supply or the system?

 

[nenenmahicon]

Also I am having the same problem

Do we have the same Power Supply?