Board Thread:False Info and Speculative Discussion/@comment-31291010-20170212164403/@comment-4091815-20170222213220

It's not explicitly stated, but  Corey apparently was a natural chimera meaning he had two sets of DNA within his body. His story is presented before the heroes work out the "natural chimera" theory. Since they knew already that he was altered, they did not include him in the list of potential chimera's and we don't have details of his condition.