Going meta and using the (potentially) available data such as humans in form of uploads, is a step made in attempt to minimize the amount of data (given explicitly by the programmers) to the process that reconstructs human preference. Sure, it's a bet (there are no universal preference-extraction methods that interpret every agent in a way it'd prefer to do itself, so we have to make a good enough guess), but there seems to be no other way to have a chance at preserving current preference. Also, there may turn out to be a good means of verification that the solution given by a particular preference-extraction procedure is the right one.