sync_binlog different for master and slave
Yes, as MySQL replication happens logically (either statements or rows are replicated) most of the options can be different between masters and slaves.

In particular, your configuration makes quite sense in several scenarios- you want your slaves to be faster than the master to avoid replication lag. You sacrifice this way consistency of the binary logs- something you may not want to do on the master (assuming it is a SPOF for you), but allowing the slave to get corrupted/loss file writes if it crashes (or maybe you do not care about that binary log at all on the slave).