Earlier quoted context omitted.
Macs used to require a physical step in addition to the software setup to modify the boot ROM. I think it was something along the lines of load firmware update which initiates a reboot, after reboot press and hold the power button until there was a loud beep from the computer, then the firmware update could proceed. Not convenient, but more secure.
That's resetting the PRAM and was required on old macs for some of the fimrware changes to actually take place (since the firmware was cached).
PowerPC Macs (in the 2000s, before the switch to Intel) did indeed require a manual step to update Boot ROM/firmware - a different mechanism than resetting the PRAM. You'd run the installer, then either shut down or reboot the Mac. As it booted, you'd either hold down the power button or the interrupt button (depending on the model) to initiate the update.