On this page: https://logging.apache.org/log4j/2.x/manual/configuration.html
There is the following sentence:
"The additivity attribute may be assigned a value of true or false. If the attribute is omitted the default value of false will be used."
Additivity controls the inheritance of appenders from parent loggers, correct? There are examples in the documentation that say will you will get duplicate logging if you don't set additivity to false (if you are setting the same appender at the root and on the logger). That implies that the default additivity is true, which would be consistent with logback, log4j, etc.