Even if your userspace is pretty fast, some necessary initialization happening before the kernel is even loaded means the you probably never get lower than 6-8

Even if your userspace is pretty fast, some necessary initialization happening before the kernel is even loaded means the you probably never get lower than 6-8 seconds. There is a lengthy EEPROM issue thread about that for the Pi4: https://github.com/raspberrypi/firmware/issues/1375 https://github.com/raspberrypi/firmware/issues/1375