This is the holy-grail in TradFI, not sure if it applies to fintech. It's not uncommon to hear from people who own an internal process only they know that's essentially their whole job security.
The extreme being people that produce only one report a month and that more than justifies their income + bonus.
Isn't that why you have processes to create documentation?
I would forget half the processes I use if I didn't document them all religiously. The benefit now is that I can save myself significant time by having an LLM help me write the docs.
What happens when this person inevitably leaves and they have no one who knows even a little bit about the process or tools used?