I know PM and PM+ don't do Raw rendering internally, or at least I think they don't. However, I can clearly look at files (Sony .arw's) and after a few seconds, a full size render appears. The same thing happens when I look at my Leica DNG files. The DNGs have small embedded previews (1440x960), but clearly after I load up an image, the full 42 MP image snaps into view. In the case of the DNGs, this full size image appears pretty quickly (it is monochrome camera, so no real raw rendering).
My question is what is going on here? Is this PM/PM+ using Apple's background rendering engine or is something else going on?