Connect and Disconnect Event log message ordering

Why is it possible that I see messages regarding the connect and disconnect events of clients in my event.log file out of order, where the disconnect sometimes appears ahead of the corresponding connect?

To ensure HiveMQ’s best in class performance task like logging disconnect and connect events are handled asynchronously. As a result the entries in the event.log may sometimes appear out of order.
This has no impact on HiveMQ's operation and guarantees.