This is a little complicated, but it's a question of how to punish bad behavior by the certificate issuer and SSL Labs is doing it differently than Firefox. https://blog.qualys.com/ssllabs/2017/04/05/ssl-labs-distrusts-wosign-and-startcom-certificates As you can see from the attached image, the certificate's effective validity date is before the effective date of Mozilla's ban, so Firefox treats it like a normal certificate issued by anyone else.

Thank you. That answers my question.