In the filters, why are the subjects displayed in Training Plans differently from CSoD?

Our system displays subjects differently than Cornerstone does. Specifically:

If a subject isn’t linked to any course, we simply don’t show it in the list.
If a main subject (a “parent”) isn’t linked to any course, but its sub-topics (“children”) are, we don’t keep the original hierarchy. Instead, we show the child subjects as if they were top-level categories — not under the parent.