Reimbursement of Wage Loss

Client handed me their 2020 Tax return in which they received a T4A for wage loss replacement. It was discovered in 2021 that they were overpaid in 2020. Normally this deduction would be claimed in 2021 since that is the year it was repaid, however could I claim it in 2020, The return has yet to be filed and the deduction would be matching when the income occurred?

CRA allows this for CERB, wondering if that got extended for all reimbursements.

Thank you.