Well, almost. That approach might work if the Hubitat hub had a UPS that would keep it up forever during an extended power outage. But consider the situation where you have a Rule, as you should, to cleanly shut your hub down after a few minutes of power outage, before the UPS battery dies.
The problem is, on reboot, the Hubitat hub never sees the “return to mains” event. Why? On power restoration after a power outage, the Hubitat hub begins rebooting. The Ring Extender, however, having internal battery power during the outage, sees the return of mains power and sends the Z-Wave event to the hub (and its driver), but the hub has not yet booted, so the event is lost.
I pointed this out a couple of years ago in this forum, when I also pointed out that Refresh was broken in the built-in Ring Extender driver. My solution was to have a Refresh in my SystemStart Rule to refresh all the Ring Extenders so that the mains/battery state was correct, but this didn’t work with the built-in Ring Extender driver because it’s Refresh was broken.
The Refresh in the built-in driver may have been fixed in the couple of years since, but I haven’t seen any note to that effect in the Release Notes.
So, I switched to the excellent user-contributed Ring Extender driver by Denny Page (@dennypage), which didn’t have a broken Refresh. When Denny Page saw my post about the dropped “return to mains” event, he modified his Ring Extender driver to have a scheduled refresh upon system reboot, so the refresh in a systemStart Rule is no longer necessary.
If you want to see my power fail detect and system restart rules that use a voting algorithm for 6 Ring Extenders to decide whether it’s a real power fail, or a failed single Ring Extender, or, as has happened, one of the Rng Extenders being pulled out of the receptacle when my wife vacuums, just ask.