The writing of "written" bits into flag registers that grow bit by bit from all erased to all written is a concept that is a part of the DataLight FLASH/FX flash file system. The concept also works nicely when designing allocation tables and use maps into non-volatile memory that does not support byte level erase / re-write. (Such as FLASH memory where you erase a segment (or the whole chip, please save us from that anymore).
Michael Karas