The power of the government to issue warrants has never (in the US constitutional system) implied a limit on freedom so that people may only possess things (including forms of communication) that are practically amenable to discovery of meaning by way of search via a warrant.

It just means government can, with legally sufficient justification, seize something. It's their job, if they want to understand it, to find a way to do it. Restricting communication to means which are easily subject to correct interpretation when seized is a violation of the First Amendment right to free speech and also exposes people to security risks from threats other than the lawful government, since if it can be compromised by a lawful seizure by government it can be compromised by an unlawful seizure by any other party.