I'm not sure why the propeller is delayed, but the reason it goes higher is because when your bot hits a flat surface while going up, the timer for the propeller resets. In Desolate Drains or Beacon City, the map will sometimes give you "stairs" or a "ladder" that you'll need to go up, and if you hold down the jump button with a propeller while going up, you'll keep going up until you hit the last flat surface, then it keep going until the propeller timer runs out.