I disagree. Telling the students there are three states of matter is just wrong and they have all the right to point it out. They keep that information for decades if not corrected/challenged and will give non true statements to others, their children, etc.

What the teacher instead should have said would be: "There are many states of matter, currently we know of (amount). The most common however are these three: solid, fluid, gaseous. Maybe you will encounter a fourth: plasma. The others form in very specific situations that are very outside of our everyday life. You can look them up if you want to know more. But for this class, we only focus on the three most common."

Everything is correct, everything is clear. The scope has been set. Teacher still looks knowlegdeable and reliable. And most importantly: does not lie, tell false facts, he provides options for individual interests and builds trust and does not offer himself for attacks on his position by misusing the trust of the students by telling them factually false content.

Relying on groveling students is morally very bad as that's no relationship based on trust and respect for the pupils and can easily be challenged, like in this example. You would only be offering yourself for failure and risk your "dethroning", which is a bad foundation to build on from the beginning.