There are other use cases for full 1080p PIP besides 3-D. Ala a "work print" that runs simultaneously with the feature film: you could choose to just watch the movie, or watch the movie with the work-print in PIP mode, or then "swap" the windows so now you have the work print in full 1080p with the feature-film mimimized, or then turn off the PIP window with the feature film and just watch the work print in full 1080... and then change your mind again... all during uninterrupted disc play with your 24-bit lossless soundtrack.
