The attached indicates he has no concept of what the firewall rules on an OpenVPN interface actually do. What he is telling you to do is pass any connection that ARRIVES into that OpenVPN circuit into your firewall.
The exact opposite should be done. An OpenVPN client to a provider such as PIA should be treated as a WAN, with only specific traffic passed inbound. If you can receive port-forwarded connections at all.
Nice of him to promote my NO_WAN_EGRESS technique, though. It's the only way to be sure.

