maven-javadoc-plugin only generates doc for the packages exported in the module-info.java file

Question

Is this normal? I want the plugin to generate doc for all packages. Here is part of my pom.xml:

<plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-javadoc-plugin</artifactId>
                <version>3.6.3</version>
                <configuration>
                    <charset>${project.build.sourceEncoding}</charset>
                    <locale>zh_CN</locale>
                    <show>private</show>
                </configuration>
                <executions>
                    <execution>
                        <id>attach-javadocs</id>
                        <goals>
                            <goal>javadoc</goal>
                        </goals>
                    </execution>
                </executions>
</plugin>

a part of structure of my project: idea project

module-info.java:

module com.chaldea.visualparsing {
    requires javafx.controls;
    requires javafx.fxml;

    requires org.controlsfx.controls;

    opens com.chaldea.visualparsing to javafx.fxml;
    exports com.chaldea.visualparsing;
}

generated doc: result

Is there a convenient way to make it generate doc for all packages? Just like the doc generated by Tools->Generate JavaDoc... in Idea. idea result