Yes - I commented out the addModule and the FrameworkBootstrap does not get the list of modules:
server.log
12:46:49,376 INFO [<mypkg>.SubsystemAdd] (Controller Boot Thread) Activating Test Subsystem
12:46:49,380 INFO [<mypkg>.FrameworkBootstrapService] (Controller Boot Thread) Test FrameworkBootstrapService - created
12:46:49,381 INFO [<mypkg>.FrameworkBootstrapService] (MSC service thread 1-15) Test FrameworkBootstrapService - started.
<NOTHING - which means that the module list is empty>
12:46:49,404 INFO [org.jboss.as.jmx.JMXConnectorService] (MSC service thread 1-16) Starting remote JMX connector
12:46:49,408 INFO [org.jboss.as.ee] (Controller Boot Thread) Activating EE subsystem
boot.log
12:46:48,559 INFO [<mypkg>.TestExtension] TestSubsystemParser --> readElement
12:46:48,561 INFO [<mypkg>.TestExtension] TestSubsystemParser --> parseModulesElement
12:46:48,797 INFO [<mypkg>.TestExtension] TestExtension --> Activating TestExtension
12:46:48,800 INFO [<mypkg>.TestExtension] TestExtension --> Activating Testpreloaded modules
12:46:48,845 INFO [<mypkg>.TestSubsystemAdd] TestSubsystemAdd --> populateModel
12:46:48,845 INFO [<mypkg>.TestModuleAdd] TestModuleAdd --> execute add
12:46:48,846 INFO [<mypkg>.TestModuleAdd] TestModuleAdd --> execute add