I only understand 50% of what you're saying (e.g. I understood none of what "use flashrom on the 4b to up sproms, in multiple devices" means), so I guess I'm under-qualified. But still interested. For some day.
My use of my Raspberry Pi 4b (the latest&greatest (as far as that may be construed)) is approaching about 4% of the potential of that little device <shrugs>
Consider it said that most devices utilise eeprom chips to house ROMs, and--we as users--are able to read, modify, and re-imprint said ROMs into these little eeprom chips.
We can thus change how they operate, to their core.
You, John, are as qualified as any other individual with regards to such things.
It's just that you've not realised the need
This lack of need is no impediment.
[edited for correct OP attribution]
One day you will become brave, and relinquish your inherent need to grasp control over off-the-shelf endeavours.
When your mind eventually imprints the "Oh! My!", you will surely find yourself free from the fear of straying Off The Reservation