They posted a link to their blog post down in the comments of the gist…

We also want to address the Bug Bounty program associated with this case. Although the researcher did initially submit the vulnerability through our established process, they violated key ethical principles by directly contacting third parties about their report prior to remediation. This was in violation of bug bounty terms of service, which are industry standard and intended to protect the white hat community while also supporting responsible disclosure. This breach of trust resulted in the forfeiture of their reward, as we maintain strict standards for responsible disclosure.

They failed to mention that the report was closed for being out of scope. Any reasonable person would expect that to mean a remediation was not coming. So really he didn’t give up his bounty because he wasn’t getting one to begin with.

Edit: cause autocorrect is dumb.