that the outcome of this event with 100% certainty.

There are unknowns that you, the shooter or the reporter have no idea about.  What is the probability that the primer, propellant, or the bullet may not meet the specification?  Yes, a sniper round is of a very much higher quality than normal ammunition.  But no manufactured product is 100% defect-free 100% of the time.  If you are an engineer working in the real world, you will know that. 

What is the behavior of the exploding apple?  Have you modeled it?  Or have you at least collected empirical evidence by shooting several apples and observing the results in the high speed film?  What is the behavior of the wooden stick when struck by a high speed projectile?

You do not know everything.  Which is fine.  No one knows everything.  So you take mitigation to guard against something unexpected happening.  What kind of mitigation you should take is proportional to the potential risk that may result.  If the potential risk is an eye injury or a loss of finger / hand, then you take correspondingly appropriate mitigation.

In this case, an appropriate mitigation is to put the apple on the stick and to put the stick on the ground.

If you do not think this way, then you will not be able to work as an engineer in a regulated industry (such as aviation, automotive, and medical)  in the US or EU.