The issue cloned for upstream from an EAP6 bugzilla.
It seems that in case that of using hornetq for implementation of object store (configuration of transaction subsystem via <use-hornetq-store/> tag) the native library (AIO) is used automatically without necessity of user confirmation.
For EAP 6.0.1 was decided that native library can't be used without explicit customer configuration request. Please check discussion on bug #900591.
The NIO should be used until customer defined otherwise.
The configuration option is missing in TM and after the adding it the EAP configuration should reflect fact that the default behaviour should be NIO.