on page 14 of the Veeam Endpoint Backup user's guide it says the following:
"[For Microsoft Windows Server Edition] If an application on the computer uses transaction logs to maintain the database consistency, Veeam Endpoint Backup automatically truncates transaction logs upon successful backup."
"Important! The Veeam Endpoint Service runs under the LocalSystem account. On Microsoft SQL Server 2012, this account does not have necessary permissions to truncate transaction logs. If you want Veeam Endpoint Backup to automatically truncate transaction logs, you need to manually add the LocalSystem account to a group that has the SQL Server System Administrator rights."
From what I read in the manual VEB should truncate transaction logs to "maintain database consistency". This may mean that it will do so for SQL Server but I haven't tested this...