From a purely technical perspective: SFS fills info->id_DiskState with the partition identifier (SFS\0) instead of the disk state (which should be DOS\0 for a validated disk),
According to the include file, it should be the number 82 for a validated disk.
struct InfoData {
LONG id_NumSoftErrors; /* number of soft errors on disk */
LONG id_UnitNumber; /* Which unit disk is (was) mounted on */
LONG id_DiskState; /* See defines below */
LONG id_NumBlocks; /* Number of blocks on disk */
LONG id_NumBlocksUsed; /* Number of block in use */
LONG id_BytesPerBlock;
LONG id_DiskType; /* Disk Type code */
BPTR id_VolumeNode; /* BCPL pointer to volume node (see DosList) */
LONG id_InUse; /* Flag, zero if not in use */
}; /* InfoData */
/* ID stands for InfoData */
/* Disk states */
#define ID_WRITE_PROTECTED 80 /* Disk is write protected */
#define ID_VALIDATING 81 /* Disk is currently being validated */
#define ID_VALIDATED 82 /* Disk is consistent and writeable */