I would agree. The BIOS/UEFI POSTs the system, and then passes execution to another program (usually a bootloader). At that point, the BIOS is no longer perfo

I would agree. The BIOS/UEFI POSTs the system, and then passes execution to another program (usually a bootloader). At that point, the BIOS is no longer performing the tasks that an OS does. It's not scheduling tasks for the processor or handling I/O at all. Instead, it switches to what's basically an ACPI interface with functions that can be called by the OS. It's like an old TSR program.