If you check the actual specifications of the carbon filter you will find that it probably reduces the chlorine about 50-25%, if flowed at the rated capacity. However, during filling, you are probably filling at twice that rate. In testing, hose-end filter reduce the chlorine 8-22%. You can check this by getting pet store aquarium strips and measuring before/after.That makes perfect sense. Our tanks have only been "used" for ten years at the most, so they should be good for some time yet.
We filter all water on the way in with a carbon filter so there should be little or no chlorine. We also find that the filter removes the smell and taste from the plastic water lines used at most marinas.
So far, so good. We do use your process every spring plus ensure the tank contents are turned over at least biweekly.
Chris
So yeah, it's kind of false advertising.