>OpenVPN looks like a regular tls stream - difficult to distinguish between that and a HTTPS connection.

I thought openvpn had some weird wrapper on top of TLS that makes it easily detectable? Also to bypass state of the art firewalls (eg. China's gfw), it's not sufficient to be just "tls". Doing TLS-in-TLS produces telltale statistical signatures that are easily detectable, so even simpler protocols like http CONNECT proxy over TLS can be detected.