Guest request for date change - impact on cancellation terms

Because of the latest local lockdowns I have guests asking - at quite short notice - to put back their stay to a later date.

Our cancellation policy is "Flexible", i.e. if the stay is less than 42 days away, they can't get  refund.

My question is, if I allow them to change to a date which is more than 42 days in the future, will they then get back the option of a full refund? If so I might as well just refund them as allow them to change.

Can't find the answer to this anywhere.