The investigating authorities aren't being defrauded though; making someone's job harder isn't fraud. Google or Amazon could be committing other crimes,[1] but not fraud.

[1] If they actually violated a gag order, which realistically they won't. In all likelihood there's language to ensure they're not forced to commit crimes. Even if that wasn't explicit, the illegality doctrine covers them anyway, and they can just ignore any provisions which would require them to commit crimes.

This is a bizarre reddit-brained legal theory.

Almost all crime requires some form of lying, at least by omission and often of the explicit sort. Fraud though, is much more narrow than "they deceived but also crimed"... and anyone saying otherwise should be so embarrassed that we never have to hear their halfwittery ever again.