The underlying issue here has been covered many times before.
The Omega 2+ has an ill-chosen flash chip, which cannot expose its full capacity unless operated in a 4 byte mode which is incompatible with the configured expectation at boot.
There is no actual working poweroff command, and there never has been one. However, programs that reboot without putting the flash chip back in a boot compatible mode end up hanging in a tight loop at boot, giving the impression of being sort of "off".
Also note that unexpected reboots, such as triggered by a watchdog will also result in a hang, rather than a successful boot.
As the Omega 2 (non +) flash chip fits entirely in 3-byte addressing mode, it should not experience this problem.
Flash chip commands can be found in the relevant data sheets, as well as the U-Boot and Linux Kernel sources.