Under Load Balancing Sink Processor section, it says:
processor.selector.maxBackoffMillis (default 30000)
I don't see that property in the code, but I do see in AbstractSinkSelector this prop:
maxTimeOut (default 30000)
So it appears that we just need to rename "maxBackoffMillis" to "maxTimeOut" in the user guide for the Load Balancing Sink Processor.