Answer:
Beyond just CIP, verifying that a customer has the legal right to use an assumed name is just a good business practice. Suppose that I want to open an account titled "Brian Crow D/B/A The Red Cross" you don't verify that I registered that assumed name and then you proceed to allow me to deposit checks payable to the American Red Cross. Down the line, your institution is sued by the people your customer swindled into making donations.