> security by obscurity thing... What am I missing here?

You are looking at the problem from the wrong direction.

If you build a honeypot, to trap hackers, does it behove you to explain what the bait is, and how the trap works?

Know your customer, fraud detection heuristics, finger prints, behavioral triggers are all areas where banks, and financial institutions need to keep the sauce secret. Telling the other party "how" you catch them just gives them the steps of what not to do.