I suppose it was part of an attempt to retcon some time elements from the previous game: the first Police Quest, if I remember correctly, took place around 1984-1985, according to dates given within the game itself. The second game tried to bring events closer to the year of the game’s release (1988), so it changed some dates – but obviously, nobody kept track of this to make sure it goes all the way (the third game, I think, also pushes the entire timeframe a few years forward). I suppose such mistakes are more obvious when it comes to games that take place in the “real world”, like PQ, as opposed to games like King’s Quest or Space Quest.
