Another disadvantage is that they use a whole lot of water. Much more wasteful than current toilets, or even the older models.
On a semi related tangent. Where does the water come from to flush one of those public toilets that doesn’t have a tank? Is it a large volume of water in a pipe in the wall?
They just tap directly off the water lines and use the water pressure. If there happens to be no water pressure, there will be no flushing at all.
The pipes are a lot bigger in diameter than your typical household pipes of 1/2 or 3/4 inches. Allows a bigger ‘whoosh’ when it is tapped,