This says to me that they intended to “game the system” with Corral being game day inactive on the 53 while being the 3rd QB and Zappe being the 2nd QB called up from PS. With the NFL closing the book on that opportunity, they would now either need to have all 3 guys active to use all 3, or only have Mac and Zappe active as a PS elevation while Corral was inactive, and they couldn’t use him as the “3rd QB” for a free roster spot. Because of that, they probably felt that Corral was wasting a roster spot so they may as well bring Zappe back back to the 53 and be able to PS elevate someone else.
They may also feel somewhat secure in Corral making it to the PS knowing that they were the only team that submitted a claim for him. Of course, Corral has to agree to sign instead of maybe going back to Carolina’s PS, but he little chance of being more than the QB3 there. He has a chance of beating out Zappe in NE.