You might find this of use:
https://forums.developer.nvidia.com/t/custom-initrd-for-nx/232508/15
Jetsons do not have a BIOS. Adding a BIOS would increase components, increase power consumption, and increase price. It might be worth it if the Jetson did not need to be efficient on power use and physical size. Otherwise you wouldn’t need all of those partitions (you’d still need what a desktop PC has for a solid state drive).