Under ERISA, a qualified retirement plan is a trust, held by a trustee. The beneficial ownership regulation does not apply to trusts.
ERISA also has a specific list of entities that are eligible to serve as trustees, among them, banks. If the trustee is a bank, then it's the bank opening the account and banks are excluded from the definition of legal entity customer. (Not partially excluded, excluded.)
In a previous thread another BOLer reported that the Helpline said to identify an employee of the bank trust department as the control person. I suggest you call the Helpline and see what they tell you.
In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.