Sonuvabitch, I had not read your comment and literally guessed this as an explanation, goddamnit.

Yeah, doing an actually good reduction down from the many channels in a theatre... that takes a lot more work than basically just smashing all the channels together haphazardly like a teen learning how to do audio levelling for their first youtube video by just flattening them all real quick...

... But that level of skill/work is apparently now just industry standard?

I keep running into media where ... even if I am using a 5.1 or 5.2 or 7.1 or 7.2 setup... its still all fucking wrong, and I have to whip up my own audio equalization script with various layers and activation thresholds... to fix it... because even though the media i am viewing claims its 5.1+ mixed... it isn't, its only a flattened 2 or 2.1.