Jack was "done" after being defeated by Sulong Duke and Neko.
Low and behold, he came back.
That's pretty much what Zoan awakening is implied to do. No matter how much you knocked down and defeat an awakened Zoan, they will get back up and keep coming.
Of course Oda can just go the route of not giving the Calamities awakening, but that's rather suspect considering these are some of the Strongest Zoan users in the World, meanwhile the Jailer beast of Impel Down have it.
Like when else is the perfect opportunity for Oda to use Zoan awakening? In another arc down the road, with less reputable Zoans?