The Banana PI M1 Armbian build is a "Developers Only" build that is not officially supported.. A "Developers only" message is clearly stated when SSH'ing in. If Armbian doesn't support their OS build, the OMV project cant' support it either.
What you're referring to, "power management control" and other hardware characteristics are clearly an Operating System and / or a hardware issue. OMV, as an application that installs on top of the OS, can not change the OS or hardware characteristics. As an example, an Odriod HC4 "reboot" in OMV's power options doesn't work. An HC4 will shut down but it won't physically (or logically) disconnect from power. To "reboot" it's necessary to physically toggle the power input. (However, the reboot option is still in OMV for hardware that supports it.)
If there's an answer to your M1 question, you might have a better chance of finding it in the Armbian Forum.
Finally, it should be noted that external hard drives have quirks of their own. Some external enclosures will power down (or power up) drives completely absent from OS commands and, in some cases, they filter out ATA drive commands and SMART data. In short, there's the potential for a number of extraneous factors related in your issue.