This is an output from dumpe2fs:
root: ~/# dumpe2fs -h /dev/sdb3 | grep -i 'fragment|block size' dumpe2fs 1.39 (29-May-2006) Block size: 4096 Fragment size: 4096 Fragments per group: 32768
Is this related to disk fragmentation?
No. ext3fs doesn't support block fragmentation so a one byte file will use a whole 4096 block.
On the opposite, for example UFS supports four fragments in a block so small files won't fill a file system as fast as they will do on ext3fs.
This is unrelated to disk fragmentation which is about file data blocks not being contiguous and sequential.