Futher reading suggests that one reason you might want to do this is to boot a custom firmware directly off the SD card. The Kobo can run from the external SD card instead of the internal MicroSD, which was no doubt an important feature during development and testing. See:
https://www.mobileread.com/forums/sho...6&postcount=20 https://www.mobileread.com/forums/sho...3&postcount=30 https://www.mobileread.com/forums/sho...0&postcount=37