Not really. They turned it on for an increasing number of customers during a single week and then turned it off for most of them, but still ended up with more IPv6-enabled customers than before. As explained in the Cloudflare blog post [0], this is common when testing IPv6 deployement before complete rollout.

[0] https://blog.cloudflare.com/ipv6-in-china/

No. The Chinese state firewall can't easily measure the true level of IPv6 and we don't completely know why our measures have fallen. There is no strong evidence it's in decline there is only evidence our measurements are unable to reliably track things.

Most measurements are over https. If they intrude a fake TLS certificate in the flow (for instance) which is common in strategic DPI inside secure channels the web blot won't fetch properly.

We've started looking at tshark captures to see if we can see partial connects.