That language is being used to justify all sorts of unethical behavior by the police, often flagrantly unconstitutional, usually at minimum illegal, and almost always the times it's not obviously illegal, it should be (the laws should be changed).

I don't know if it's from lack of regular interaction from the police but I find a lot of people online are under the mistaken impression that the constitution or law is guarding the rights of people in the USA. Cops get away with violating the constitution and breaking the law multiple times every day - sometimes in ways the supreme court has allowed, such as by lying to you, or tricking you into thinking you have to voluntarily give up your rights. Combine that with a completely overwhelmed court system that leads to something like 90% of people taking plea deals, and the absurd concept of "mandated minimums" and sentencing requirements that judges blindly follow, and you've got a legal system that's nothing like what people represent online.

So I feel "well it's suspicious but of course they should get a warrant" is pro-surveillance state, not anti.

That would mean, essentially, that they could not do anything at all with your packages unless they already have a reason to suspect you of a crime, and that even then, they have to have a reason to believe that a particular package is involved in said crime and even say beforehand what they expect to find in it.

Now, on to the specific scenario at hand. You might argue that that is too stringent, that no crime can ever be proven under that framework, and you may say it shouldn't preclude x rays and drug dogs and what not, I might even agree with you. But that as well as any other reasonable concept of justly handling suspicion precludes randomly opening peoples packages and keeping money by construing the simple presence of money as evidence that a crime maybe was committed and they get to keep it whether there was or wasn't a crime there. Even by the most lax framework of how to handle suspicion and searching property that is outrageous.