how to get consistent binlog position LOCK TABLES FOR BACKUP + LOCK BINLOG FOR BACKUP

as per this article this is the xtrabackup workflow:

LOCK TABLES FOR BACKUP … copy .frm, MyISAM, CSV, etc. … LOCK BINLOG FOR BACKUP UNLOCK TABLES … get binlog coordinates … … wait for redo log copying to finish … UNLOCK BINLOG
I don’t have enough knowledge on how “FOR BACKUP” is working under the hood and i’m a bit confused in “get binlog coordinates” step. If LOCK BINLOG FOR BACKUP is after LOCK TABLES FOR BACKUP there is not a risk of getting a position newer then mysql data?