There was an attempt at crafting a regex to block IPv6 domains for Netflix due to their tunnel/proxy block (HE IPv6 tunnel). It doesn't work too well 
.
PiHole appears to respond with the IPv6 instead of the Null reply as configured in pihole-ftl.conf.
Preference is to configure via pihole-ftl.conf due the to complexity and lack in consistency with Netflix IPv6 hosted content.
Mar 21 14:37:36 dnsmasq[20211]: query[A] ipv6-c010-mia006-ix.1.oca.nflxvideo.net from 10.61.6.50
Mar 21 14:37:36 dnsmasq[20211]: forwarded ipv6-c010-mia006-ix.1.oca.nflxvideo.net to 2620:fe::9
Mar 21 14:37:36 dnsmasq[20211]: query[AAAA] ipv6-c010-mia006-ix.1.oca.nflxvideo.net from 10.61.6.50
Mar 21 14:37:36 dnsmasq[20211]: forwarded ipv6-c010-mia006-ix.1.oca.nflxvideo.net to 2620:fe::9
Mar 21 14:37:36 dnsmasq[20211]: validation result is INSECURE
Mar 21 14:37:36 dnsmasq[20211]: reply ipv6-c010-mia006-ix.1.oca.nflxvideo.net is 45.57.103.134
Mar 21 14:37:36 dnsmasq[20211]: validation result is INSECURE
Mar 21 14:37:36 dnsmasq[20211]: reply ipv6-c010-mia006-ix.1.oca.nflxvideo.net is 2a00:86c0:2103:2103::134
Thanks.