Maven unpack transitive dependencies' JAR to a folder - maven

Question

I have two maven artifacts in my private repository, com.test.Parent and com.test.Child. Child is dependent on Parent.
The only thing I want Maven to do is to download the Child jar and everything it depends on, and then unpack it to a directory.
I was able to put together a pom.xml that downloads the Child by calling mvn clean dependency:unpack, however in order to download the transitive dependency I had to manually include it in the pom.
What I want is to call, for instance maven initialize and my required dependencies would be downloaded. What I have now is this:
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-dependency-plugin</artifactId>
<executions>
<execution>
<id>unpack</id>
<phase>initialize</phase>
<goals>
<goal>unpack</goal>
</goals>
<configuration>
<artifactItems>
<artifactItem>
<groupId>com.test</groupId>
<artifactId>Child</artifactId>
<version>1.2.3</version>
<type>jar</type>
<includes>**</includes>
<excludes>META-INF/**</excludes>
<outputDirectory>somepath/sources</outputDirectory>
</artifactItem>
</artifactItems>
</configuration>
</execution>
<execution>
<id>unpack-dependencies</id>
<phase>initialize</phase>
<goals>
<goal>unpack-dependencies</goal>
</goals>
<configuration>
<excludeTransitive>false</excludeTransitive>
<includes>**</includes>
<outputDirectory>somepath/depend</outputDirectory>
</configuration>
</execution>
</executions>
<dependencies>
<dependency>
<groupId>com.test</groupId>
<artifactId>Child</artifactId>
<version>1.2.3</version>
<type>jar</type>
</dependency>
</dependencies>
</plugin>
</plugins>
However, when I run mvn clean initialize, only the Child files are downloaded and unpacked.
POM file of com.test.Child contains this:
<groupId>com.test</groupId>
<artifactId>Child</artifactId>
<version>1.2.3</version>
<dependencies>
<dependency>
<groupId>com.test</groupId>
<artifactId>Parent</artifactId>
<version>7.8.9</version>
</dependency>
</dependencies>
Do you see any problem with the setup? The endgame is that developers can just download one pom.xml, run mvn <something> and all the dependencies will be automatically downloaded and unpacked to a certain structure.
Thanks
Edit:
When I delete my local Maven repository and run this pom, both Child and Parent are downloaded. So the dependency is there, but Parent is not picked up by the unpack-dependencies goal.

Answer 1

I solved the issue by moving the <dependencies> block outside <plugins>. So the final POM structure is:
<project>
<build>
<plugins>
<plugin>
...
</plugin>
</plugins>
</build>
<dependencies>
<dependency>
<groupId>com.test</groupId>
<artifactId>Child</artifactId>
<version>1.2.3</version>
</dependency>
</dependencies>
</project>
But if anyone can explain to me why this helps, that would be appreciated.