I've experienced this on ORD-PEK a few years back, before 1Ks preboarded. They started boarding Group 1 through Door 1 and Group 2 (followed by other groups) through Door 2. Between F, J, 1K, and platinum, almost exactly half the plane was in Group 1. The tail end of Group 1 -- which included me (had to get my passport checked at the last minute) -- boarded at the same time as Group 4.

I appreciate the desire to be more efficient. But early boarding is a defined privilege of certain ticket classes and status classes, and screwing up the system so that those folks board with Group 4 is not cool.