Thank you for letting us know.
The need to erase all user-saved data comes up time to time, for example when Eddystone password is changed, stored to flash and forgotten. Adding store to flash functionality is near the top of my TODO anyway, I could bump it up on priority.
I’m looking at https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk52.v0.9.1%2Fbledfu_memory.html, I’d think that the “erase app” should delete everything starting from the end of it’s own memory and ending at the beginning of bootloader.
I’m horrible at remembering to follow-up on development, if you don’t hear from me by the next week end please ping me and let’s see if we’d have that erase app ready for testing