Sure, there’s lots of room for LLMs in helping to do clerical work, HR, that kind of thing. I was actually thinking of the direct management of funds and investments. So yeah, like probably all businesses, the ancillary functions can probably improve productivity using Generative AI with a minimal hit to quality.
You are right about the clerical work, but even pure finance is a lot more than 'direct management of funds and investments'. Have a look at Matt Levine's Money Stuff newsletter for a taste.
And I'm not quite sure why you mention determinism in the grandfather comment? Finance people have been using Monte Carlo simulations for ages. (And removing non-determinism from LLMs by fixing the seed of any pseudo-random number generator used wouldn't really change anything, would it?)