Section 603 - Settlor's powers; powers of withdrawal(a) While a trust is revocable, rights of the beneficiaries are subject to the control of, and the duties of the trustee are owed exclusively to, the settlor.(b) During the period the power may be exercised, the holder of a power of withdrawal has the rights of a settlor of a revocable trust under this section to the extent of the property subject to the power.