Perhaps you are simplifying. But the information above is not actually accurate. It is what most people say. But....most people seem to have this wrong.
Sponge dampens. That actually does mean that sponge makes the ball go slower. However, that also makes it so you can swing harder.
So, here is how this works. Thinner sponge is better for more direct contact like smashes, drives and drive loops. With that kind of shot you have more control and the ball will go faster. But thinner sponge causes the ball to impact the wood sooner, so, for a player whose spin contact is less developed, it makes harder to LEARN how to spin. Someone who has solid spin contact can use thinner rubbers and still spin the heck out of the ball. But someone learning will bottom out when trying to spin and end up hitting a flatter shot.
Thicker sponge makes it easier to Learn spin contact and, when you are spinning the ball, it allows you to let the ball sink deeper into the topsheet and sponge without impacting the wood of the blade so:
1) you have a bigger window for making spin contact without bottoming out,
2) someone with good spin contact will be able to get the ball to sink deeper so the topsheet wraps around the ball more fully and grabs the ball more fully, so you get more spin.
For someone who is learning to spin the ball, thicker sponge makes that easier, but it makes it so you have less control ON MORE DIRECT CONTACT (like drives and smashes). For someone who knows how to spin, thicker sponge gives you more control because it allows you to get more spin and to control the ball with that extra spin. It ALSO allows you to swing much harder while spinning the ball, so, the end effect, is, when spinning the ball, you can hit a faster shot while getting more spin with thicker rubbers. The faster shot is not because the rubber is faster. The faster shot is because you can put more force into your swing without losing control PROVIDED you are spinning the ball.
So, the issue is more complicated than most people present. But there is something in what I explained above that caused Werner Schlager to say that any person training and wanting to get to a high level looping, should never use anything thinner than max. Now he was talking about elite kids. So, maybe that is not always the case. But if you want to improve your technique and your looping skills, it would be worth understanding what caused Shlager to say that.