Getting back to the OP's question.
Where should the finger go and why? What do the trainers say? For LEOs, what is your policy?
1) The finger should rest on the trigger the moment the sights rest on the subject. There will be no more time to move the finger if needed, it will disturb the sight picture, etc.
2) The finger should remain along side of the frame until the decision is made to shoot. Otherwise you may shoot accidentally.
3) The finger should enter the trigger guard but not contact the trigger.
"Always keep your finger off the trigger until the sights are on the target."
"Never let your muzzle cover anything that you are not willing to destroy."
These basic firearms safety rules still apply in a gunfight.
The finger does not enter the trigger guard until the decision to shoot has been made. The sights don't go on the target until the decision to shoot has been made. Therefore, sights on target=finger on trigger. Why make it any harder?
Sights on target does not mean the gun pointed in the general direction of the BG. Sights on target means the gun is in firing position with hard focus on the front sight and a good sight picture of the specific part of the BG that we are trying to hit (head, thorasic triangle, exposed shoulder, etc.).
Why you you want to hold someone at gunpoint with the sights on the target and not shoot them? If you don't need to shoot, the gun should be at retention position (or low ready if you have trained that way). By holding the sights on target you are occluding your vision of the BG's hands and waist area.
None of this means that you have to shoot the BG once your sights are on target and your finger is in the trigger guard. If you make the decision to not shoot, the sight comes off the target, the finger goes off the trigger, the safety goes on and the gun comes back to retention/ready.
Once you train yourself correctly, it becomes easier. If you train making shoot/no-shoot decisions, it becomes easier.
Interesting; dont really agree with it....but interesting.