Since you can sue anybody for anything, anything that you do exposes you to potential liability. *grin*
The only part of the screw that is 'doing any work' is the part that extends from the head to the part that is engaged in the thread, and perhaps a tinsy bit past to support the last bit of engaged thread. The rest of the screw is just 'extra'.
One could argue that using a longer screw than necessary is 'bad workmanship' because the extra length of screw could puncture conductor insulation. If you go and change all of these screws to the supplied length, and damage a wire, then you would be exposed to potential liability for following poor installation practise.....
-Jon
