The law makes it clear that the rules are only suspended in the customs zone of the airport and within 100 miles of the airport. They seem to follow that. The checkpoints you see in Washington state or down near the border with Mexico do not show up around denver or dfw. The reality is bad enough we don't need to exaggerate it. And they can't just grab every phone as they walk around LA either, they have to signal their dog to alert on you to give them probable cause...
The rules are not suspended within 100 miles of the airport, it’s only land and sea borders. (Look it up.) The person you were responding to is wrong and we need to push back against this becoming accepted “folk wisdom” or it will lead to more rights violations.