My first time to encounter this, not sure I understand. So they can refund now without first notifying the author?
there can be different reason to refund as like the customer has purchased duplicate license (2 license) but they need single license and customer can open a support ticket for getting refund for 1 license. another reason can be customer can dispute refund and won the dispute. to get more info you should to contact author support.
Also double check that you’ve not had an extended license sale with the same invoice details. Had that a few times, when the buyer got a regular license, needed an extended one and support have sorted that for them.