First of all thank you very much for your time and interest in doing the analysis and mentioning the workaround for the brown-out problem.
We will discuss on this internally and will do the necessary steps to enhance the documentation..
I also wonder how firmware upgrades using the Copying method is intended to work. It always copies from one fixed location to another.
So if I where to upgrade the bootloader component to a newer version and that version used a more flash, I would not be able to produce applications that could be loaded on devices using the older bootloader.
Yes. You are correct. It is required to build the Applications with the Bootloader that is present in the devices running in the field.
In case the Bootloader is updated in the newer application, the Bootloader that is running in the field devices should be upgraded first and then build the applications with the newer Bootloader version.