The actual physical address on the storage chip and the physical address from the operating system's perspective don't have much to do with another. For harddrives, "un-partitioned space" means that there is a physical "chunk of metal" that is unused.
However, that's not the case for SSDs. SSDs dynamically remap "OS-physical" block numbers to whatever they want. (Preferably addresses that have never been used before or that have been discarded/trimmed. If there aren't any available, perhaps to the address that was previously used for the same block number.)