I don't consider Pavel Durov, Tucker Carlson, or X/Twitter to be trustworthy sources of information...
...but I do find it plausible that gag orders could target individual engineers, which would be even more concerning than those targeting an organisation. If a project's leaders don't know about a back door, then not even a warrant canary will help.
If this is already happening in the US, what regulation or law is being used to justify it?