Ah ok I thought you applied patches to OpenWrt u-boot.
I see the changes in the usb code of uboot in the commit you linked.
I will try to send a PR myself, and I will ask you to test a uboot I compiled, as all my USB drives work fine in uboot.
Does the uboot in the nsa310b have the same issue? I think it should. Can you try the same USB drive in the nsa310b and see if it works or not?
In my nsa325, the noise happens because it's screwed to the metal plate in the back. The fan was nearly silent if removed from the NAS. The metal plate was making a lot of noise with just a little vibration from the fan.
I placed some soft rubber between the fan and the metal plate, and used metal wire instead of the screws to hold it in place. Now it's not noisy.
I can't slow the fan down, I'm using old drives that heat a lot, I need the air movement.
Yes it would be useful.