Even though openvpn uses TLS, AFAIK it's used on top of some wrapper which makes it trivial to detect and block. At least in my experience it's the one of the first protocols to get blocked.

Openvpn is trivial to see , what you need to do is wrap it in stunnel

Yeah I suspect they know they can never block everything but if they can block 98% of "casual users" they've probably reached their goal. They will just put out propaganda that the other 2% technically apt people who get around it are conspiracy nuts, western civ sympathizers, traitors to mother russia, etc.