They didn't introduce any errors _into_ a certificate. They affected the certificate chain, but not the certificate directly. I'm certain this is how their own lawyers view this.
This is going to get hilariously legal. A certificate from GlobalSign or anybody else is the product of the chain, if the chain isn't there and the cert isn't valid it's no more valid than a self-signed one.
Tell me again, anybody, why we trust these people?