Merely using port 443 to evade censorship is no longer effective, if it ever was to begin with.

Since the stratum protocol is unencrypted, it is trivial for censors to deploy filters that block the protocol if they want to block bitcoin mining. It is also trivial for them to deploy DNS filtering to prevent miners' networks from resolving the domain names of known mining pools, and if miners decide to use unencrypted public DNS resolvers, to hijack their DNS requests to either prevent them from resolving pools' domain names, or feed them fraudulent IP addresses to connect to. And then there are other more sophisticated forms of internet censorship that are not only in use by state-level censors, but also by enterprise networks—e.g., deep packet inspection, etc.