How to grant [DatabaseBackup] SP execution privilege to a none sysadmin role user?

[JParkACR]

I (SA) granted the Ola hallengren's [DatabaseBackup] SP execution privilege to a none sysadmin role user.
But the user failed to make a backup due to the 'xp_ss_delete' or 'xp_fileexist' system sps.

I found '@ExecuteAsUser' parameter in [CommandExecute] SP, but there is no documentation about this parameter and couldn't figure out how to use it.

Is there anyone who can successfully grant the [DatabaseBackup] privileges to a none-sysadmin role user??