That is a feature of most modern power supplies, so you can charge your phone, ect with USB.
You can try hidden setting to disable wake via USB. On the MAIN page of the BIOS, press control + F1, the screen will flash, then go into power page and disable wake via USB and save/apply and see if that shuts off USB with the board. If not, it's because your power supply is modern, motherboard and power supply manufacturers see this as a "Feature"