Just to clarify: "with a repayment of 1/3 of the deferred 2020 retirement distribution"

This is not the first or even third time it is being stated backwards. You likely mean, "to report the second of the three taxable income amounts." There is no repayment and no distribution was deferred. Just the reporting of the taxable amount, because the taxpayer did not elect to report the income from the one distribution all in the year of distribution.