When you FIRST pull out the Ballistic knife your player has to pull the knife apart and it takes a little time. If you go ahead and pull the Knife out right when you spawn he will do this for you and you wont have to do it later on. For example if your in a battle with someone and you need to switch to your secondary to finish him off there will be a little wait while he pulls the knife apart. If you go ahead and do it when you spawn it will be ready as soon as you switch to the secondary later on that life and will save some time and sometimes your life. Hope this helps