Before the rule, an entity account could be opened without ever naming a human being. Financial institutions must now collect the ownership prong, any individual owning at least a quarter, and the control prong, one executive or manager with significant responsibility.
The US Corporate Transparency Act added a parallel reporting regime in which many companies report beneficial owners directly to fincen, though its scope has been narrowed by litigation and rulemaking.
For traders operating through an LLC or a family entity, this is the reason account opening asks for personal documents from members who never intend to trade.
Related: customer-identification-program, fincen, customer-due-diligence, bank-secrecy-act, anti-money-laundering