Plain old active carbon will get rid of chlorine. Chloramine is tougher to get rid of. I wouldn't be surprised if it did get rid of it too though.
But the carbon doesn't remove the chlorine until it runs through the filter. It would already have been in contact with the fish for a fair amount of time, and it would probably kill off or prevent bacteria colonies from establishing in the media.
The claims are true, but worded in a way to mislead inexperienced or uneducated fishkeepers.