While you are right in that those two resolvers show some strange AAAA record, those aren’t the resolvers in use by Google and CF.
Google Public DNS IP addresses
The Google Public DNS IP addresses (IPv4) are as follows:
- 8.8.8.8
- 8.8.4.4
The Google Public DNS IPv6 addresses are as follows:
- 2001:4860:4860::8888
- 2001:4860:4860::8844
Cloudflare
- For IPv4: 1.1.1.1 and 1.0.0.1
- For IPv6: 2606:4700:4700::1111 and 2606:4700:4700::1001
So where you found those addresses beats me.
Found this page explaining some more around that. It mentions something about that specific prefix (64:ff9b::/96).
Still, it has nothing to do with Virtualmin though.