They absorb any extra water such as from when fuel separate begins and moisture from the atmosphere, but there is a limit on how long this absorption works.
Theoretically you would eventually run your engine and burn it off.
If left unburned you have water absorbed by the Ethanol and water absorbed by the additive that breaks down to even more water.
Think of it this way, if additives were the ultimate answer, it would be added-in at the terminal where the Ethanol is added to the non-ethanol gasoline.
