Why isn't there a maven extensionManagement element for extensions?

We use an extension in our projects and until now put the extension under the pluginManagement section of the maven parent pom:

<pluginManagement>
    <plugins>
        <plugin>
         <groupId>org.apache.maven.extensions</groupId>
         <artifactId>beer-maven-lifecycle</artifactId>
         <version>1.0-SNAPSHOT</version>
        </plugin>
     </plugins>
</pluginManagement>

But this results in the following warning:

[WARNING] Failed to retrieve plugin descriptor for org.apache.maven.extensions:beer-maven-lifecycle: Failed to parse plugin descriptor for org.apache.maven.extensions:beer-maven-lifecycle (/somerepo/org.apache.maven.extensions-0.0.0.jar): No plugin descriptor found at META-INF/maven/plugin.xml org.apache.maven.plugin.PluginDescriptorParsingException: Failed to parse plugin descriptor for org.apache.maven.extensions:beer-maven-lifecycle (/somerepo/org.apache.maven.extensions-0.0.0.jar): No plugin descriptor found at META-INF/maven/plugin.xml

Which makes sense since it is an extension and not a plugin. But there is no extensionManagement element. So what would be a way to handle this? E.g. this project also describes the issue (lines 78-80)...