It’s a custom protocol that uses SSL/TLS for key exchange and such, so it can be detected. It’s actually causing huge problems for many large Russian companies, as it’s common to use those protocols for remote access, work, etc.

As mentioned in the article you need something like “Shadowsocks” to avoid protocl blocking, since it fully disguises the traffic as standard SSL/TLS. Which was created for, and is still used to circumvent this type of blocking in “the great firewall of china”.