When Creating a CSS Snippet to modify ObsidianMD's bullet list's bullets, why does the class '.cm-list-4' work?

Question

Can someone explain to me why when modifying the style of bullet lists, you can only go three levels deep using .cm-list-n where n is level?

The following doesn't work:

.cm-list-4 .list-bullet:before {
    content: '\25AA';
}

This, however does:

.HyperMD-list-line-4 .list-bullet:before {
    content: '\2024';
}

I'm still relatively novice in CSS styling. Using the Developer tools, I see that at the fourth level it cycles back to using '.cm-list-1' -- is this an inherent mechanic of how Obsidian creates the lists?

CSS Inspection View of Fourth Level Bullet

Is .HyperMD-list-line a parent of .cm-list-n and has precedence such that .HyperMD-list-line-4 overrides .cm-list-1 at the fourth level or something along those lines?

I attempted to dissect the source CSS and app.css to understand better how ObsidianMD applies styling but I'm still novice at CSS so my understanding is a bit shaky.