config per execution: system property visible in wrong/later execution.

I use the plugin in build as follows:

     <plugin>
	<groupId>org.codehaus.mojo</groupId>
	<artifactId>exec-maven-plugin</artifactId>
	<version>3.0.0</version>
	<executions>
	  <execution>
	    <id>install-pkg</id>
	    <phase>pre-integration-test</phase>
	    <goals>
	      <goal>java</goal>
	    </goals>
	    <configuration>
 	      <mainClass>eu.simuline.arithInOctave.RunOctave</mainClass>
	      <systemProperties>
		<systemProperty>
		  <key>target</key>
		  <value>${project.build.directory}${file.separator}</value>
		</systemProperty>
		<systemProperty>
		  <key>artifactId</key>
		  <value>${project.artifactId}</value>
		</systemProperty>
		<systemProperty>
		  <key>artifactVersion</key>
		  <value>${project.version}</value>
		</systemProperty>
		<systemProperty>
		  <key>assemblyId</key>
		  <value>${assemblyId}</value>
		</systemProperty>
	      </systemProperties>
	    </configuration>
	  </execution>

	  <execution>
	    <id>uninstall-pkg</id>
	    <phase>post-integration-test</phase>
	    <goals>
	      <goal>java</goal>
	    </goals>
	    <configuration>
 	      <mainClass>eu.simuline.arithInOctave.RunOctave</mainClass>
	      <systemProperties>
		<systemProperty>
		  <key>artifactId</key>
		  <value>${project.artifactId}</value>
		</systemProperty>
	      </systemProperties>
	    </configuration>
	  </execution>
	</executions>
      </plugin>

I run always the same class but I want to distinguish the class from the properties.
But in post integration test still property 'target' is visible.
Thus in this case, instead of install and uninstall, we have install twice.

I expected that for each execution separate properties are passed.
A bit like for surefire plugin and failsafe plugin which allow to configure these also separately.
Maybe this is not a bug and one has to use arguments instead.

Still then in documentation, there shall be a hint on that configs can be used globally
or per execution, but then not system properites.

Reproduce the two java executions from the issue, using the install-pkg and uninstall-pkg configurations and their systemProperties. Start by tracing how per-execution configuration is handled for the Java goal. Done means determining whether the properties are isolated between executions and either correcting that behavior or documenting the limitation and workaround.