Well, flash memories are a variant of EEPROM. But many code flash memories have one or more multiples less wear resistance than the traditional EEPROM memories. So the code flash region can work well for storing configuration. But it is often impossible to store runtime state information. And some code flash memory also contains EEC, i.e. error-correction, making it impossible to perform multiple writes to a sector without an erase in between. For flash memory without EEC, it's possible to just write parts of the sector, and leave the rest of the sector empty. Then perform more writes later. This is a common method for flash file systems, to reduce the number of write/erase cycles.