The VPS is running socat only and just doing tcp forwarding. There is a shared haproxy also run by their same host, sitting in front of the VPS and is handling

The VPS is running socat only and just doing tcp forwarding. There is a shared haproxy also run by their same host, sitting in front of the VPS and is handling the TLS. I encourage you to read the article fully. They probably should have said "VPS provider" instead of VPS for the TLS bit.