This is probably due to my own ignorance, but I've only seen "preference utiltarianism" used to denote the idea that an individual's utility should be calculated from their own preferences (as opposed to some external measures of their happiness, virtue, whatever). Is it standard terminology to use the term to refer to this way of making interpersonal calculations of utility as well?

In any case, isn't there a problem with making this technique well-defined? If I would prefer to be me instead of my neighbor, then we'd conclude that I have higher utility, but if he would also prefer to be himself instead of me then we'd reach the contradictory conclusion that he has higher utility, and yet such pairs of preferences may be simultaneously true more often than not!