Comando que você usou --delete-during
apagará os arquivos no lado de recebimento /mnt/usb0/backup/partition2
No entanto, verifique seu --exclude-from
arquivo /etc/rsync-exclude.txt
tem o nome test.txt
nele.
Você também pode usar as opções abaixo,
--delete-before receiver deletes before xfer, not during
--delete-during receiver deletes during the transfer
--delete-delay find deletions during, delete after
--delete-after receiver deletes after transfer, not during
--delete-excluded also delete excluded files from dest dirs