For example, I receive one of the listed COVID-19 benefits, like the CERB. I applied for it, but I wasn't entitled to receive it, so I have to pay back some portion of it. If it's an income-tested benefit, maybe my income was a bit higher and I had to pay back a portion of it.
I receive an amount in, say, 2020 and I repay it in 2021. Both the income inclusion and the deductions would be in 2020, so it becomes a wash.