Set it to Native. That’s how it is supposed to work. I have set it up that way on MTNL IPv6.
That test is bugged.since last 3 days the ipv6-test.com website shows that icmp (v6) is not reachable. Earlier I used to get 19/20 , but now I get 17/20
All firewall settings are same as when the icmp (v6) was reachable.