Let me answer that a different way.....
your kids can be independent one year and dependent another year, based on the circumstances of that year. They just can't pick and choose when they feel like it. Let's say they live at home, do not go to school and are unemployed, they certainly could be your dependent this year. Then next year they make more than $4300, they can't be your dependent, then the year after that they are unemployed again and they could be your dependent.
the question they are asked on THEIR tax form is CAN they be a dependent, not were they a dependent. The answer to CAN is going to be consistent with the IRS rules and not their whim.
run your scenario through this IRS tool and it will tell you if they CAN be a dependent.
https://www.irs.gov/help/ita/whom-may-i-claim-as-a-dependent
if they are doing this to get stimulus, be careful and wary.
ps and to clarify @Bsch4477 's comment. What he meant was YOU get a choice to claim them as dependents or not, the IRS doesn't care. but the children DON'T get a choice - the answer to whether they CAN be claimed doesn't change whether you claim them or not.
