Lily pipes are designed to make a little swirl on the water surface to get rid of surface scum.
Unless you have a massive amount of outlet pressure when using the recommended pipes, you're not going to see much of a swirl. I get a decent surface ripple in my 20L with a 2215 with 13mm lily pipes. The only noticeable one I've seen was in a well-known 60-F thread on here in which there was an Eheim 2215 attached to 9mm pipes. Normally you would would use 13mm pipes for that filter outflow. Concentrated flow = whirlpool.