The refunding bonds may be made registerable as to principal and may bear interest at a rate not to exceed the maximum rate authorized by the Bond Authorization Act, as amended at the time of the making of the contract, payable at such time and place as may be provided in the bond resolution. They shall remain valid even though one or more of the officers executing the bonds ceases to hold his or their offices before the bonds are delivered.
     With respect to instruments for the payment of money issued under this Section either before, on, or after the effective date of this amendatory Act of 1989, it is and always has been the intention of the General Assembly (i) that the Omnibus Bond Acts are and always have been supplementary grants of power to issue instruments in accordance with the Omnibus Bond Acts, regardless of any provision of this Act that may appear to be or to have been more restrictive than those Acts, (ii) that the provisions of this Section are not a limitation on the supplementary authority granted by the Omnibus Bond Acts, and (iii) that instruments issued under this Section within the supplementary authority granted by the Omnibus Bond Acts are not invalid because of any provision of this Act that may appear to be or to have been more restrictive than those Acts.