The others have dealt with the bulkhead verses interior partition issue. As regards the details of the deck plan, I think you've answered your own question. Clearly there are freshers and plumbing (and stoves or some means of preparing food, and pantries/fridges or some means of storing food, and sinks/dishwashers and trash cans or some means of cleaning dinnerware/kitchenware and dealing with refuse, and laundry machines, and so forth). Just as clearly, they're not on the deckplan. The deckplans offer a rough layout of the ship, not a detailed blueprint. It is for the gamemaster to fill in the needed details.
