grails 2.5.x does not evict oldest version of conflicting library - grails

Question

Using grails 2.5.1 with, in BuildConfig.groovy
[...]
grails.project.dependency.resolver = "maven"
[...]
I have a grails application including 2 custom plugins (hosted on our nexus maven repo): gw-mr:1.7.3-RELEASE and gw-mr-security:1.7.4-RELEASE
These 2 plugins depend on the same library, mr-client. However gw-mr lags behind gw-mr-security and was not rebuilt for some time, but its code has not changed. In the meantime, gw-mr-security has been bumped, and uses a newer version of the common library: mr-client. So if we take a look at the POM of gw-mr:
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<dependency>
<groupId>irrelevant</groupId>
<artifactId>mr-client</artifactId>
<version>3.6.5-SNAPSHOT</version>
<scope>compile</scope>
</dependency>
[...]
And looking at the POM of gw-mr-security, we see:
[...]
<dependency>
<groupId>irrelevant</groupId>
<artifactId>mr-client</artifactId>
<version>3.9.0-SNAPSHOT</version>
<scope>compile</scope>
</dependency>
[...]
So, indeed, gw-mr-security declares a later version of mr-client than gw-mr.
When I include these 2 plugins in the host grails application, I can see something really weird, when I run grails dependency-report compile:
[...]
+--- irrelevant:gw-mr:1.7.3-RELEASE
| \--- irrelevant:mr-client:3.6.5-20170921.151252-2
+--- irrelevant:gw-mr-security:1.7.4-RELEASE
+--- irrelevant:gw-rest:1.7.8-RELEASE
[...]
So, even though my app declares both plugins in its dependencies (BuildConfig.groovy):
[...]
compile "irrelevant:gw-mr:1.7.3-RELEASE"
compile "irrelevant:gw-mr-security:1.7.4-RELEASE"
[...]
grails still does not examine both transitive dependencies and evicts the dependency coming from gw-mr (3.6.5-SNAPSHOT) for more recent version included in gw-mr-security (3.9.0-SNAPSHOT).
Of course, when I include the transitive dependency explicitly in my host application:
[...]
compile "irrelevant:mr-client:3.9.0-SNAPSHOT"
[...]
Then the right library is packaged in my war.
Is my assumption wrong, that grails evicts older versions of the transitive dependencies included by plugins?
Thanks for any insight.