Well, first of all WinpkFilter x86 standard build (NDIS hook based) you probably downloaded from this site ignores IPv6 protocol (you still can see incoming IPv6 packets as they are also delivered to IPv4) and works with IPv4 only. Though it can be easily extended to support IPv6, but it require rebuilding driver binary. Such sort of modification is available to licensed users.
x64 standard build also available from this site is based on NDIS IM driver and by default it works with both IPv6 and IPv4.