Regarding unmount, see USB Power shutdown method? And Hard drives? - #18 by vpeter
But iirc disks are already parked by CE when using suspend/sleep.
Regarding usb port power reset during boot, could be an overload of 5V USB power rail. HDD is not the only consumer on internal 5V rail, depends on other USB port consumers and internal consumers. Often the overall 5V power is limited to e.g. 2A for all USB ports, but not communicated well. Ask Ugoos for details.