You only need that hose if you have made your mind up to use the pink stuff to winterize. I also had a Starcraft trailer before the Airstream. My pump was under the bathroom sink, was very easy to get to and had the bypass hose already installed. Winterizing was a breeze.
I "moved up" to my 06 25 FB and found that the pump did not have the hose attached. As a matter of fact, the location of the pump would make it very tough for me to add the bypass so I called the local dealer and asked. They informed me that they winterize all their units with compressed air. This is what I do and after 5 winters have had no problems at all. If I had a real choice, I would probably go back to the pink stuff method as it would give me a bit more confidence all things considered. Of course, whichever method you use, it has to be done correctly. You can read about all of this in a bunch of threads out there.