Thank you for raising this!
I was always wondering about the flag_boot_rootfs=1 and flag_last_success=1 for firmware=0 mentioned in the Wiki:
If I'm not wrong, OpenWrt is always installed in mtd8 regardless of the initial stock value detected by cat /proc/cmdline, hence NVRAM should always be pointing to firmware=0 after OpenWrt is installed (am I wrong?)
Could someone also review the bootloader code flags logic to confirm it?