ModuleSet does not support classifier

I am trying to define a toplevel assembly using the docs here:

http://maven.apache.org/plugins/maven-assembly-plugin/examples/multimodule/module-binary-inclusion-simple.html

I have two submodules that create a sub-assembly from dependencies and a war file. The sub-assembly is creating using assembly:attached bound to the 'package' phase.

When trying to reference the sub-assembly using a moduleSet there is no way to specify the classifier for the subassembly.