Correct. I found a gravity filter “ZeroWater” that is a five stage filter including ion exchange and will remove Total Dissolved Solids (TDS). Fluoride is a dissolved solid and while the website and literature won’t specifically say that fluoride is removed, since it is a DS it should be removed. When you order a pitcher it comes with a TDS meter to measure before and after filtration.
A “TDS” meter is only measuring the electrical resistance of the water.