UI layout is modular and patchable. Engine architecture isnt. If the UI were truly immutable, the More Columns mod wouldnt exist
Modders have already proven the CAS UI is not hard‑coded into the engine. If a small modder can expand the columns in an afternoon, the game devs can absolutely do it too.
If EA wanted this feature they could literally adopt the existing mod, integrate it, and maintain it the same way they maintain every other UI element that breaks each patch. The fact that they dont tells you the limitation isnt technical, its a design choice they have decided not to revisit. And that choice directly reflects on their competence in UI design.