backups starts even if the credentials doesn't match

I was trying the new xtrabckup 2.1.3 rpm on rhel6 with percona server 5.5.28 to perform a backup.

It just starts the backup even if the user exist and doesn't care about if the credentials match or even just with empty string password=' '

xtrabackup --version
Warning: xtrabackup: ignoring option '--innodb_adaptive_hash_index' due to invalid value 'OFF'
xtrabackup version 2.1.3 for Percona Server 5.1.59 unknown-linux-gnu (x86_64) (revision id: 608)

mysql -V
mysql Ver 14.14 Distrib 5.5.28, for Linux (x86_64) using readline 5.1

xtrabackup --defaults-file=/home/mysql/my.cnf --defaults-group=mysqld101 --user=dba --password=anything --backup --target-dir=/nfs-backup/restore/backup/

Warning: xtrabackup: ignoring option '--innodb_adaptive_hash_index' due to invalid value 'OFF'
xtrabackup version 2.1.3 for Percona Server 5.1.59 unknown-linux-gnu (x86_64) (revision id: 608)
xtrabackup: uses posix_fadvise().
xtrabackup: cd to /home/s_game_br/data/dbs
xtrabackup: Target instance is assumed as followings.
xtrabackup: innodb_data_home_dir = /home/mysql/data/ib_dbs/
xtrabackup: innodb_data_file_path = ibdata1:10M:autoextend
xtrabackup: innodb_log_group_home_dir = /home/mysql/data/ib_log/
xtrabackup: innodb_log_files_in_group = 3
xtrabackup: innodb_log_file_size = 268435456
xtrabackup: using O_DIRECT
130606 8:58:34 InnoDB: Warning: allocated tablespace 1115, old maximum was 9
>> log scanned up to (17320357009575)
[01] Copying /home/s_game_br/data/ib_dbs/ibdata1 to /nfs-backup/restore/backup/ibdata1
>> log scanned up to (17320357045819)
>> log scanned up to (17320357053195)

Is that a bug ? or just for the backup it doesn't care about the credentials and only be needed when its doing the --prepare and applying the log.

Thanks. and sorry if there is already an issue about it , didn't find in the bug list with my search keywords.

Chandu