HI Q,
I recall that there was a statement about low starter air pressure may cause max motoring to be below 25%.
Certainly the autostart logic has a minimum N3 for starting threshold and a max motoring detector based on the rate of change of N3, but for a manual start the decision must be more difficult.
VnV
by the way the early engines didn't have autostart because no-one had ordered it. When a customer wanted it there was near panic in the systems team trying to cram it into the box.