When you go for number 2, your poo will not directly fall into the watery bowl of the toilet which is connected to the sewer system, but it will land on a nearly-flat area with a small volume of water under your butt. So, you are given the opportunity to see, examine, and “appreciate the beauty” of your poo before flushing it away.
On my first day in The Netherlands, I immediately got the key to my room in a former-asylum building which has been turned into a housing for international students. The housing company installed this kind of toilet in the building. I joked with my fellow international students that this is a “welcome gift”, a “small cultural introduction lesson” from the country.
There are small issues. First, obviously the smell. In “common” toilet, your poo falls into watery abyss, so it will not be so smelly. In Dutch toilet, well… you know. Gross! Ew! >.<
Second, flushing. It requires massive force of water to remove the poo from the shelf to the sewer system. If your poo is stubborn, well… Ew! >.<
However, most toilets in The Netherlands do not have inspection shelf; it seems like they have switched to “common” or “normal” toilets.
I also encountered a few of this when I visited Vienna (in Austria). A friend of mine informed me that it is actually not just “Dutch toilet”, but “European”. If any of you know more about it, feel free to clarify or correct me.