Configuration requires execution block

Currently the mojo is only executed if there is an execution block in the configuration like this:

<plugin>
<groupId>de.smartics.maven.plugin</groupId>
<artifactId>maven-buildmetadata-plugin</artifactId>
<executions>
<execution>
<phase>initialize</phase>
<goals>
<goal>provide-buildmetadata</goal>
</goals>
</execution>
</executions>
</plugin>

Why is this execution block required and the mojo is not bound to the phase as tagged by javadoc tags?

• @goal provide-buildmetadata
• @phase initialize