Yes, forwarding rules for VPN <> Internet. Check out /etc/wireguard/wg0.conf:
PostUp = sysctl net.ipv4.conf.%i.forwarding=1 net.ipv4.conf.$(ip r l 0/0 | mawk '{print $5;exit}').forwarding=1
PostUp = sysctl net.ipv6.conf.$(ip r l 0/0 | mawk '{print $5;exit}').accept_ra=2
PostUp = sysctl net.ipv6.conf.%i.forwarding=1 net.ipv6.conf.$(ip r l 0/0 | mawk '{print $5;exit}').forwarding=1
PostUp = iptables -A FORWARD -i %i -j ACCEPT; iptables -t nat -A POSTROUTING -s 10.9.0.0/24 -o $(ip r l 0/0 | mawk '{print $5;exit}') -j MASQUERADE
PostUp = ip6tables -A FORWARD -i %i -j ACCEPT; ip6tables -t nat -A POSTROUTING -o $(ip r l 0/0 | mawk '{print $5;exit}') -j MASQUERADE
PostDown = iptables -D FORWARD -i %i -j ACCEPT; iptables -t nat -D POSTROUTING -s 10.9.0.0/24 -o $(ip r l 0/0 | mawk '{print $5;exit}') -j MASQUERADE
PostDown = ip6tables -D FORWARD -i %i -j ACCEPT; ip6tables -t nat -D POSTROUTING -o $(ip r l 0/0 | mawk '{print $5;exit}') -j MASQUERADE
ip r l 0/0 | mawk '{print $5;exit}' prints the interface name of the default route, hence should be eth0. As you can see, the sysctl-wise IP forwarding is enabled as well, althought only for the particular interfaces, not for all.