It has been a very long time since I was punished by having to fly a Jet Ranger....but my point about the valve operation is correct in that it is can be open in varying amounts during normal engine operation....correct?
It starts fully open....and is fully closed by about 92% I am thinking.
Rapid acceleration of the engine will also cause it to open unless I am mistaken.
I have far more experience with PT-6's and Lycoming Engines than I do Allisons.