Hello Ilias
When we say that NTPv4 has some improvements that also support the IPv6 address family, we are not stating that only NTPv4 can be encapsulated within an IPv6 packet. In your packet capture, an NTPv3 packet is encapsulated within a UDP datagram, which in turn is encapsulated within an IPv6 packet.
The phrase “supports the IPv6 address family” simply means that some mechanisms and fields in the NTP header have been modified to take into account the use of IPv6 addresses, but this only refers to background processes such as MD5 hash generation, and the use of site-local multicast for IPv6, for example. Take a look at the NTPv4 RFC found below that details these changes:
Ultimately, you won’t see any particular change in the configuration of NTPv4 compared to NTPv3, even if you use IPv6 addresses, as you have done in your example.
It may also be helpful to take a look at this cloudshark capture that shows the communication of an NTPv4 client with an NTPv3 server:
https://www.cloudshark.org/captures/30ea2044f399
I hope this has been helpful!
Laz