I think the problem is that feature must not working in your version of VDM.
I am not even sure that it was implemented at the time we have release it.
If I am not wrong you also have Spark Dubstep
. Did you try with it?
Again, an update of both will be released soon and this will definitely work on 1.7.
Concerning AU vs VST, this is because AU does not let plugins send MIDI to other tracks so if you want to do that with AU version you have to do create a virtual MIDI port with the IAC driver wich is not needed with VST version.