[Ok, so in other words, you do not have anything useful to contribute to this thread?
No, quite frankly he is saying from your lack of real world experience, you have not had anything useful to contribute to the safety of our air system or even flying an airplane. You cut StuSEL's part out about mentiong this point.
Here is why I say this. If you think the hold short line is a place where safety stops on checking controls are free and clear or ANY before takeoff check list items, you are sadly mistaken. Lots of things can happen from the first control free and clear check and the time one taxi's out to the active runway.
Co-pilot / passenger could have shifted their legs in such a way where they obstruct the yoke / rudders. My knee pad could have shifted such a way to obstruct the yoke. The yoke clip holding departure procedures / approach plates could have shifted in such a way to obstruct the yoke (getting tangled on the external mic coiled wire).
The above three examples have happened to me in the real world. So if you see me waving my elevator and call it show boating so be it, but one can never "trust but verify" enough when it comes to flying an airplane. This only shows your lack of experience in aviation.
Finally, PIC DECIDES when items are to be checked and RE-CHECKED, not the hold short line. Once I cross the hold short line to take off, I am expected to depart without undue delay. Nothing says I can't do safety checks like check controls, check DG to ensure it matches the runway heading while I am on the active runway.
I've said in the 8th reply of this thread that this topic you posted is off topic for these forums and seems like others are coming around to my way of thinking. Really time to get this thread shut down so my email alerts will go back to normal.
(edited to add enough to sentence with trust and verify)