First, you only need the medical form if you are requesting special equipment or services for medical reasons. It's not like a physical that the kids need for camp.
The requests can be extremely varied--confirming the need for a handicapped accessible cabin, a refrigerator to keep medications (in addition to the standard beverage cooler), distilled water for CPAP machine, administration of IV medications by the medical/nursing staff, etc. If you don't have a medical need, you don't need to do this form. Your TA should have the fax number. Keep a copy for yourself just in case they suddenly can't find it after boarding. And call a few days before the cruise to be sure that everything is in order.