I disagree very strongly with your last comment - I think it is flippant and ill-considered. The repair times allowed for 'warranty' repair are less than what is actually required to do the work (typically about 80% of the time actually required). This is common practice across all manufacturers, American, Japanese, and German. The rationale, which is understandable, is that the dealer also shares some of the warranty responsibility, as they are the retail partner of the manufacturer.
The Phaeton is a new vehicle on the market, and it is not yet widely distributed. There are probably less than 2,000 in North America at this time, on average, that works out to only about 1 or 2 per dealership.
If you are asking a service technician to complete an unfamiliar procedure on a new vehicle - a darn expensive and complex vehicle at that - it is entirely reasonable to expect that the technician is going to take more time than average to complete the work. If 9.5 hours is the warranty allotment, and that represents 80% of the actual work time, then actual work time is about 12 hours. The dealership is adding 50% on to that to allow for the fact that the technician is doing this work for the first time on an unfamiliar product. That's pretty reasonable to me - in fact, I'd be damn grateful that the dealership cares enough about doing a good job the first time round to allow the technician the time that it really will require to do the job thoroughly and carefully.
In Europe, VW provides a two week training and certification course for Phaeton service technicians. That is a remarkably long course in the automotive industry. I doubt if hands-on practice removing and installing fuel tanks is part of the course.