I think what you are forgetting is that the AIM is not regulatory. From
the looks of it, it is as if you're expecting to get a violation if you
start your engine prior to calling ground. That just won't happen.

This thread has gotten out of hand. The bottom line is that if you
start your engine, then get your clearance, then call ground, it may
end up wasting your time with the engine running if there are delays.
But, no matter what, you will never get in "trouble" for starting your
engine prior to getting the clearance, or talking to ground.

Lynne