Typically not (but I guess it's possible). CGNAT is expensive to run, but carriers do it because it can be less expensive than getting more IPv4 addresses, and it's faster to add capacity than to get addresses. IPv6 addresses are very low cost and quick to ger assigned, so if you're supporting IPv6, and you run low on addresses, adding CGNAT doesn't make sense.

It's much more typical to either have cgnat IPv4 and public IPv6, or just cgnat IPv4 and no IPv6 than to have cgnat both.

In the wake of the wannacry debacle, quite a few ISPs have moved IPv6 as well behind CGNAT.

That doesn't sound quite right to be honest - do you have a source for that?

I don't even see what possible rational there could be for such a change. Most native v6 consumer already have firewalls for IPv6 in the CPE which block any incoming connections per default, so not even the misusing NAT as firewall argument applies here.

No there is basically no NAT with IPv6, apart from some very niche edge cases.

NAT is expensive.