Hello,
As per the article "K22954168", i think is it safe to use any command if the appliance mode is disabled, and the concer was only when the appliance mode enabled. as you mentioned you can go with the hald procedure, and you can check the below article as well:
"Alternatively, you can power off the system using the halt command (do not use the -p option). Once the serial console reports the device has been halted, then unplug the power to the appliance. In this case the "last power state" of the appliance is "powered on". When input power is re-applied, the appliance will automatically power on and boot."
https://my.f5.com/manage/s/article/K000132560
Thanks,