Think of it this way. With an expandable if a blade contacts the deer before the tip does the deer is more or less a stationary object thats not going to give. The blade meets that object and somthing has to give either the arrow or the deer. Im not going to get into a physics lesson but the deer isnt going to give so the arrow must. Thats why it kicks outwards. That blade that catches must push away from the arrow to fully deploy and doing so its not going to move that deer so it has to move the arrow.