Maven-Plugin's getLog() ignores -Dorg.slf4j.simpleLogger.defaultLogLevel=warn

Hi,
since Maven should supports slf4j-Logging combined with the SLF4J Simple implementation from Maven 3.1.0 onward (http://maven.apache.org/maven-logging.html).
I'm kind of wondering why the default getLog() called from a Plugin ignores the Environment-Variable ``-Dorg.slf4j.simpleLogger.defaultLogLevel=warn``

I'm currently using:
Apache Maven 3.2.3 (33f8c3e1027c3ddde99d3cdebad2656a31e8fdf4; 2014-08-11T22:58:10+02:00)
Maven home: /usr/share/maven-3.2.3
Java version: 1.7.0_80, vendor: Oracle Corporation
Java home: /usr/lib/jvm/java-7-oracle/jre
Default locale: de_DE, platform encoding: UTF-8
OS name: "linux", version: "3.16.0-33-generic", arch: "amd64", family: "unix"

Tested with different Maven-Versions and different maven-plugin-api Versions, still no success.
Any help is highly appreciated.
Thanks,

PS: Hopefully I can attach my Example-Project which can be executed by using:
mvn clean install && mvn clean package -Pdemo -Dorg.slf4j.simpleLogger.defaultLogLevel=warn