Jack you are not thinking tactically.
The biggest advantage a leader has is that they are already winning and they can set the pace. And other than a horse having the drop on you, one of the biggest disadvantages is that you do not have eyes in the back of your head (you cannot be looking around the whole time)
Let's say I am a driver who knows their horse well and knows their opposition well too.
I know that my horse and his main opposition are capable of running a final half of 54 provided nothing too crazy has happened in the first half
We are inside the half mile and I know that I have a handy gap on my main opposition (they have been caught out) and I know that before they will react to my move I will have a couple more metres (the nature of initiator v reactor)
I could forfeit this extra advantage of surprise and just do a rubber neck and try building the pace to maintain my gap on them, knowing I am still a 70% chance of winning. There is also that slight chance that when you take your eyes off them, they put in a spurt and close the gap (gaining the initiator meters)
OR
I could take advantage of their mistake and my knowledge of how fast I can get to the finish and how fast they are capable of going and increase my winning chance to 90%.
It makes me think of the brilliant drive of Glen Craven on Keayang Steamer when he beat Smoken Up in the Horsham Cup this year. It was a reverse of this situation in that Keayang was right with Smoken but Glen caught Lance out by taking the initiative by accelerating quickly earlier than Lance expected which has become the recipe for beating SU since (the champ does have a fair excuse - 11 of them)