Just in time for the holiday season, Google products has tightened up their “Products” search. In the past things seemed a bit scattered and not completely logical. My guess is that some of the experimentation with Google Base has led them to include certain fields. The ability to add your own fields to a Google Base product gives them quite a bit of information regarding important fields for particular item types.
Google Products might just be best suited as a mobile application. This new search interface leads me to believe that it is going more in that direction.