mkfs.ext4 e mkfs.vfat com o mesmo arquivo badblock me dão um espaço diferente

Question

Eu tenho um pendrive de 256GB com setores defeituosos, e eu os obtenho com este comando:

sudo badblocks -wsvf -o 256GB.txt /dev/sdc

Mas quando eu uso este arquivo ( 256GB.txt ) para formatar o pendrive, eu obtenho um espaço disponível diferente dependendo do tipo de formato.

Com o fat32 eu ganho 203 GB de espaço disponível:

$ sudo mkfs.vfat -F 32 -v -n 256GB -l 256GB.txt /dev/sdc -I
mkfs.fat 3.0.26 (2014-03-07)
/dev/sdc has 255 heads and 63 sectors per track,
hidden sectors 0x0000;
logical sector size is 512,
using 0xf8 media descriptor, with 524288000 sectors;
drive number 0x80;
filesystem has 2 32-bit FATs and 64 sectors per cluster.
FAT size is 63985 sectors, and provides 8189999 clusters.
There are 32 reserved sectors.
Volume ID is 9029d4fa, volume label 256GB      .
50098433 bad blocks
$ df -h /media/user/256GB/
Filesystem      Size  Used Avail Use% Mounted on
/dev/sdc        250G   48G  203G  20% /media/user/256GB

Com o ext4, ganho 44 GB de espaço disponível:

$ sudo mkfs.ext4 -v -l 256GB.txt -L 200GB /dev/sdc
mke2fs 1.42.9 (4-Feb-2014)
/dev/sdc is entire device, not just one partition!
Proceed anyway? (y,n) y
fs_types for mke2fs.conf resolution: 'ext4'
Filesystem label=200GB
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
16384000 inodes, 65536000 blocks
3276800 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=4294967296
2000 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912, 819200, 884736, 1605632, 2654208, 
    4096000, 7962624, 11239424, 20480000, 23887872

...
Warning: the backup superblock/group descriptors at block 52297728 contain
    bad blocks.
...

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done     
$ df -h /media/user/200GB/
S.ficheros     Tamaño Usados  Disp Uso% Montado en
/dev/sdc         246G   190G   44G  82% /media/user/200GB

Você sabe por quê?

Obrigado

P.S .: Eu escrevi ... antes e depois de Warning: ... , porque havia muitos avisos assim.