Xtrabackup Slave Server with log-slave-updates


I have a question regarding XtraBackup and slave servers.

We have failover setup where B server is a slave from the A server. The B server has in it’s config the option
log-slave-updates = ON
Which makes it so everything run through the replication it’s also inserted on B’s binlog.

Recently we decided to enable backups through XtraBackup, and looking into the option for slave backups, there is one named --safe-slave-backup .Which stops the Slave agent in order to do the backup without interference for a “consistent slave backup”.

Given that we are using the log-slave-updates option, it’s this really necessary? As I understand, the issue at first it’s that if during the backup process the Slave Agent is inserting transactions, which aren’t logged in the binlog, the backup can end up in a inconsistent state as it has no idea about what the agent is doing.
However, when the log-slave-updates option is enabled, XtraBackup should handle those transactions by default with it’s usual mechanic of keeping track of the binlog.

Is that so? Or even if I have the log-slave-updates I need the --safe-slave-backup option for a consistent backup?

Thanks in advance!