Notwithstanding Section 16572 to the contrary, if on or before June 30th of the fiscal year in which the state project is completed the district has received a final apportionment under Sections 16000 to 16207, inclusive, or if at any time thereafter the district receives a final apportionment under Sections 16000 to 16207, inclusive, the amount of the apportionment to the district under this chapter then remaining unpaid shall, upon request of the district, be added to the principal amount of the apportionment made to the district under Sections 16000 to 16207, inclusive. Thereupon the apportionment made to the district under this chapter shall be deemed to be an apportionment made to the district under Sections 16000 to 16207, inclusive, and subject to repayment in the manner therein prescribed, except that no interest shall be charged or collected upon the amount which is added to the principal amount of the apportionment made to the district under Sections 16000 to 16207, inclusive. For the purposes of Section 16083, any amount added to the principal amount of an apportionment pursuant to this section shall be deemed to have become final and disbursed to the district on the date the state project is deemed completed pursuant to Section 16571.