Some people put the final focus on the cueball. Stephen Hendry and Ronnie O'Sullivan do it.
When I focused object ball last, the pause at the back was when I made the final shift of focus from cueball to object ball. Now that I take my final focus back to the exit wound on the white, the process follows a similar patern. When the cue is moving forward my eyes are on the white. Got that after bumping the cueball accident ally a few times(in the beginning).
So on the final draw back I am confirming that the tip is taking the prescribed line through the cueball to launch it to the contact point that has been locked in on the object ball. At the back my eyes shift to the white and exactly where I want to strike it. Then my final focus is where the cue tip would exit the back of the white if it was immovable. That accounts for my pause at the back. Sometimes the confirmation takes a little longer. When it takes too long, it's time to stand up and sort out the solution then start over.