This is just your speculation. A bunch of other people in this comment tree say it's not about outcomes in an unequal society being worse than outcomes in a (hypothetical, possibly unachievable) equal society with the same resources. Instead it's about a hardwired biological stress response that people lower in the social hierarchy have when they observe people higher up.

So before we go lecturing about how it "isn't that complex" let's make sure we understand what this thing is that's supposedly not that complex.