When I started doing RLHF work on financial reasoning, I assumed my edge would be the domain knowledge: that having actually bootstrapped a credit curve would let me spot the errors quickly. Partly true. But the real difficulty is subtler.
A model that gets a DCF wrong is easy to correct. A model that gets the number right through a chain of reasoning that would break on any adjacent problem is much harder, because the output looks perfect. You have to grade the reasoning, not the answer, and that means articulating why you personally believe something, which most finance people have never had to do explicitly.
My internships taught me the answers. This job is making me explain them.