It is possible. You have not mentioned what kind(s) of income they received. If they have mostly Social Security and only a smaller amount of other income with some tax withheld, they might be getting back all the tax that was withheld. Without details we cannot tell you more.
Possibly, especially if most or all of their income is from Social Security. Seniors also get a large Standard deduction. If their 2021 situation will be similar, they may wish to stop the withholding.