It depends on whether this "ITF" account is a simple account in the name of an individual, ITF an identified beneficiary, which is recognized by law in your state as the functional equivalent of a POD account. If that's the case, the "beneficiary" has no legal claim on the account during the life of the account owner (not typically referred to as a "custodian"), and I would not assume any interest of the beneficiary in the withdrawal.
On the other hand, if the account is actually holding funds in a fiduciary arrangement in which the "beneficiary" has a legal claim on the funds and the "custodian" is a fiduciary, you should assume that the custodian is acting on behalf of the beneficiary, since that is the expectation in a fiduciary relationship.
You've described the account using what appear to be conflicting terms. You'll have to sort out the actual nature of the account (using legal counsel if necessary) to make an informed decision concerning completion of the CTR.