Good question, Jack. I'd guess it depends on the severity of the disabilities. Obviously if a ship has 100 motorized chair passengers aboard, it would tax the crew's abilities in an emergency much more than if the number were 20. And then on the other hand they have to tread lightly else find themselves in trouble with the government for discrimination.
I do know that at my place of employment - a federal installation - we have to have X number of handicapped parking spaces based on the total number of employees. Handicapped slots are added when our workforce increases in size, and vice versa. But on any given day, not every person with a handicapped decal on their car is guaranteed a special parking slot. Perhaps the same thing goes with the number of handicapped cabins on ships, and along with that the number of significantly disabled passengers.
BTW, I have a quadriplegic niece, a good friend who is a double amputee (both legs), and one of our best employees is paralyzed from the chest down. And of course my wife spent much of the past year in a wheelchair or worse, so I am not looking at this without some level of understanding for the disabled.