Spring-loaded Dock items are supposed to save you time by allowing you to drag a file over the folder/icon. Hover it for a few seconds and the application/folder will open. Use the following command to enable these feature:
defaults write com.apple.dock enable-spring-load-actions-on-all-items -bool true
Restart Dock with the following command:
killall Dock
Revert to the default setting:
defaults write com.apple.dock enable-spring-load-actions-on-all-items -bool false
Spring Loaded item starts at 05:09