The USB drive option of a My Cloud Home does not support the safe eject option.
If your drive is NTFS, HSF+, unsafe eject should not result in a dirty bit as those file systems are more residual.
If you are using exFAT, I would power off the My Cloud Home, remove the USB drive and power on the My Cloud Home if dirty bit or data corruption on the exFAT file system is of a major concern.