What happens if stdout is redirected to the same file as a FileAppender?

DuplicateLogging.java

import java.io.IOException;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class DuplicateLogging {

    private static final Logger logger = LoggerFactory.getLogger(DuplicateLogging.class);

    public static void main(String[] args) throws IOException, InterruptedException {
        logger.info("message 1");
        logger.debug("message 2");
        logger.info("message 3");
        logger.debug("message 4");
        logger.info("message 5");
        logger.debug("message 6");
        logger.info("message 7");
        logger.debug("message 8");
        System.out.println("This goes to the console!");
    }
}

logback.xml

<configuration>
    <appender name="FILE" class="ch.qos.logback.core.FileAppender">
        <file>log.txt</file>
        <encoder>
            <pattern>[FileAppender] %date %level %msg%n</pattern>
        </encoder>
    </appender>
    <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <pattern>[ConsoleAppender] %date %level %msg%n</pattern>
        </encoder>
        <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
            <level>INFO</level>
        </filter>
    </appender>
    <root level="DEBUG">
        <appender-ref ref="FILE"/>
        <appender-ref ref="STDOUT"/>
    </root>
</configuration>

• Both appenders write to the file using separate pointers (so they overwrite each other).
• For the section that's overlapped, the console appender wins. Is it because it's slower (or faster)?

Example invocation:

bcalmac$ java -cp .:/Users/bcalmac/.m2/repository/org/slf4j/slf4j-api/1.7.25/slf4j-api-1.7.25.jar:/Users/bcalmac/.m2/repository/ch/qos/logback/logback-classic/1.1.11/logback-classic-1.1.11.jar:/Users/bcalmac/.m2/repository/ch/qos/logback/logback-core/1.1.11/logback-core-1.1.11.jar DuplicateLogging > log.txt; cat log.txt
[ConsoleAppender] 2017-07-27 22:36:58,173 INFO message 1
[ConsoleAppender] 2017-07-27 22:36:58,175 INFO message 3
[ConsoleAppender] 2017-07-27 22:36:58,175 INFO message 5
[ConsoleAppender] 2017-07-27 22:36:58,175 INFO message 7
This goes to the console!
8,175 INFO message 5
[FileAppender] 2017-07-27 22:36:58,175 DEBUG message 6
[FileAppender] 2017-07-27 22:36:58,175 INFO message 7
[FileAppender] 2017-07-27 22:36:58,175 DEBUG message 8