The cruiseline paperwork asks everyone whether they have a medical disability. If you answer, 'yes' of course they will want to know about your disability. They want to be sure they can accommodate you and they want you to know what to expect from them. Answer the forms honestly because they're for your benefit.
Believe it or not, the people who refuse to fill out the forms because they think they're too intrusive are the same ones who complain when they get on board and discover they're limited because of their disability.
Case in point: A few years ago a passenger on a cruise required a wheelchair; but didn't bring one. He expected to get one on board and also expected there would be a crew member available at all times to push him around in it. Needless to say, his cruise activity was limited.