User parameters 16KB
Duplicate this twice to make 512KB.
The duplicate copy is to support OTA update which may fail.
So maybe this is some kind of scheme where the ROM section is hardware cached from the flash to make it imitate a ROM.
Could it be:
64KB of real RAM
172KB of cached pseudo ROM?
Where the cache might consist of two 4KB hardware pages that fault in pages from the flash chip as needed?