5.1 mix got way more good stuff in it than the stereo mix
I always thought 5.1 mix and stereo mix contains mostly the same stuff, turns out I’m wrong.
The thing I’m watching right now (don’t ask), contains deep bass in the 5.1 mix (downmixed back to stereo), while the stereo mix contains none of that good stuff.
Looks like they presumed the typical stereo setup would lack the deep bass abilities so they they cut out the bass from it! (Or maybe they boosted it for 5.1, but man it sounds fabulous)