If you put an item in a dropper and drop it, it will act as if it was dropped by a player, which means there will be a delay between the moment the item is shot and the moment it becomes possible to get it.
Steps to reproduce :
-Place an item in a dropper
-Power the dropper
-Pick up the item.
Addition by Mega_Spud: Added comparison video: https://youtu.be/xyYD5DjwcPI