Jp I would like you to re-evaluate this level. If you look at the map and follow what the switches and paths do you might understand. (Read all the info bubbles.)
What happens is that if you don't get the treasure is that when you are going towards the goal you will run into a switch that raises the ball covering the goal and quickly drops it. when you get the treasure the switch is moved up so that you can't reach the goal. That is why there are those comments at the beginning of the level to hint you.
If you don't get the treasure and you move at full speed after it you would get the goal by getting just under the boulder. (That is where it is hidden)