WF Stubs - Execution Sequence

I am a bit confused with the WF Stubs, their execution sequence etc.

Scenerio: I have added custom properties to kick off all the WF Stubs (so I could know when each of them is called during various state changes) and within each WF stub I have added a MachineLogEvent to log message when the workflow started (Ex: "WF Stub Building Machine" is logged to userLog when the workfflow was called).

All workflows are "PreActivityExecution" in ExternalWFstubs.xml (default file).

Custom properties added are:

Then I request a machine from vCac portal, progress as below:

Question 1: Why was "Machine Registered" workflow not called

Question 2: Since the WF Stubs are "PreActivityExecution" -- this should have meant that "WF Stub Machine Provisioned" (logItem 30) should have been called before "Machine Provisioned" state (logItem 29) ? but thats not the case here. Am I missing something fundamental here ?

Thanks in anticipation.