Wan option "Disable IPv6" does not disable 6rd tunnel
On Foris and ReForis the option "Disable IPv6" does not disable 6rd tunnel on the Wan interface. 6rd is an opkg package that's installed by default. It automatically detects and configures 6rd functionality. Further information is described here: https://openwrt.org/docs/guide-user/network/ipv6_ipv4_transitioning#rd_tunnel_isp-provided_ipv6_transition
I think the option "Disable IPv6" should also disable the 6rd tunnel functionality. If there's anything I can do to help, please let me know.