Strange behavior with mirror-bin log patch

[AdmobDB]

We downloaded and start using the mirror bin-log patches, but the behavior is strange. Both master and slave have same version i.e. 5.0.67-d7-ourdelta44 and necessary settings for mirror bin-logs. I am trying to setup new slave from this master db server. When I start replication on slave it creates the identical bin-log file to the one on master. I have 2 questions,

1] I was under impression before starting the replication it will download all the prior bin-log files to slave, but that does not happen. It just download the recent one i.e one specified in "change master " command.
2] If I stop replication for backup or business needs like keeping slave few hours behind, the bin-log file on slave gets all the events from master starting from beginning. It does not take into account that the replication is merely resuming and do not need all the events right from beginning. Otherway if it has to do then it should overwrite and not append.

Does anyone experienced similar behavior ? Or Please comment on expected behavior. Let me know if you need additional information from our side.