Is there actually a reason why the information of the original mixing level is not provided in a file format? You gave this eye opening example with 79 mixes being 6 dB too loud on a calibrated system. The lower the mixing level, the more extreme the mismatch for a calibrated system. Why not just store this one extra number to avoid this problem? Or one could print it on the blu-ray box.BS. The levels are adjustable in the Cinema. This video aptly demonstrates this. Pay attention to the commentary from 1:53 and on. They did (as I did) peak loudness measurements in the theaters in their area (just like I did), and the peak loudness was all over the place (just like they were in our measurement project on THX theaters and screening rooms). This my friend shows that any auditorium's master volume level can be adjusted so a manager can address any volume level complaint in any auditorium in real-time. This is regardless of the mix level, of which nobody knows except the mixers. Your statement is illogical, and shows total ignorance of how things work.
You can measure how loud the mix is, but that is completely different from how loud the mix is played back. sigh! Just like I have a volume control on my receiver, a theater has a volume control on its server. I can turn up or down the volume at will, and so can a movie theater, and the link above shows this.
Anyone who has watched a lot of movies on disc knows that there are movies that are mastered quite high, and others that are mastered quite low. If it is mastered too high, you reach over and turn it down if it is offensive (Transformer movies). If it is too low, you turn it up until you are comfortable (some Disney movies). Same in a movie theater. Mastering levels have nothing to do with playback levels when there is a volume control at the playback end. This is illogical to think otherwise.