Passive Mixes and Ducking

I’ve got some questions regarding passive mixes.

Is there a way to make a sounds that belong to a child sound class push and pop the passive mixes of the parent class? When I do STAT SOUNDMIXES and fire sounds that are assigned to child classes they don’t seem to fire any passive mixes other than the ones directly assigned to that class. Also in the documentation it says that if you set the duration to -1 the passive mixes wouldn’t get applied but in my tests they clearly do.

This question arose when I was looking at the files for the Robo Recall modding kit I came across the sound class hierarchy. I saw that its SFX branch is neatly organized in low, medium, high and highest importance and that those classes each have a passive sound mix that ducks the rest of the classes depending on their importance. This sounds like a great approach in theory but it doesn’t seem to be working for me.

Is there a place I can look into to get more info about passive mixes and how they behave and interact?

Thank you for your attention.