That's scaremongering and simply false. Cgnat servers are not necessarily congested. I've been to several isps with cgnat and none of them suffered from congestion.
On a more personal note, if ipv6 were so great, their fans wouldn't have to make up things to badmouth ipv4.
On a more personal note, if ipv6 were so great, their fans wouldn't have to make up things to badmouth ipv4.