Oswald could have cycled the bolt action in that time. They even had a 65 year old weapons expert that was able to do this. That is why he had the sniper’s perch.
Right, cycling the bolt almost always means taking your eye out of the scope to do it. Yes, a bolt can be recycled in 2.3 seconds. But to reacquire the target, a moving target, all in that same time frame, impossible.
Oswald’s position was one of height. That does not necessarily make it a sniper’s perch. Anyone wanting to shoot above and away from the crowd would have selected it.