If you post something on a public forum you naturally invite criticism. If you dont want someone to criticise you then dont post.
Is the knowledge that you are sharing beneficial? Are you providing wrong "knowledge"? Do you want people to waste their money and maybe even damage their catalytic converter?
Do you know how catalytic converters work and how do they get blocked?
If you use an old grade engine oil it will poison the catalytic converter.
The catalytic converter can also get blocked due to soot and carbon.
Another way to block/damage it is by pouring something cold on a hot converter.
To unblock it you have to run the engine at high speed for an extended period of time. It increases the temperature of the converter and breaks down the deposits.
If you have bad sensors, your car runs rich, or there is some problem in the ignition system due to which unburnt fuel is entering the exhaust, you can clog your cat converter. Cat con runs very hot and when fuel enters there it burns and raises the temp even more which can melt the mesh.
If you pour your cleaner liquid (or even regular engine oil or even water) on ANY PIECE OF HOT METAL it will produce the same white smoke. Now, does that mean that it is cleaning something? I dont think so.
Lastly if you read the description here: LIQUI MOLY - Motor Oils, Additives, Car Care - Products - Catalytic-System Cleaner
It says that the product is quote " for removing typical contamination and deposits found in the intake and combustion system"
If you notice it does not say much about cleaning the cat converter (at least in the main description.)
In addition it says "Dissolves and removes deposits and contaminants such as oil, resins, adhesive residues, etc. of the intake and combustion system."
It also says "The high cleaning effect ensures a clean catalytic converter and reduces the exhaust emissions."
In short they clean rest of the system and hope that if rest of the system works well cat con wont get clogged. (It might actually clean the cat con but I personally think it is unlikely)