Why do you think NSA cares much about hiding their activities from you?
I can tell you a story. Some years ago, back in Russia, as a [naive] kid, I've developed a surveillance system for Telrad telecom exchange [ultimately for FSB]. Do you think anyone cared to do that project in secrecy? I can give you the answer. Nope.
As far as I understand NSA can legally intercept packages and can legally install undetectable surveillance devices. As long as they are not using collected surveillance data, legally they are fine and they do not absolutely have to hide their activities at all costs. Hiding large scale operation is difficult and plugging every information leak is expensive. So they are not necessarily prioritizing that. So, yes, there is a change that we simply see their activity. And yes, it could be just an Amazon bug.
During the cold war (and shortly after), this type of activity would be exactly what red-blooded Americans would say differentiated us from Russia (not hiding it, but doing it at all). Americans have constitutional protection against unreasonable search and seizure by the government.
These days you could probably drop the country and year and have trouble differentiating tactics used by the US and Russia.
It's going after low-hanging fruit to say this and while the link I'm providing is not the NSA, our government agencies seem to have a real hard time keeping secrets lately.
I can tell you a story. Some years ago, back in Russia, as a [naive] kid, I've developed a surveillance system for Telrad telecom exchange [ultimately for FSB]. Do you think anyone cared to do that project in secrecy? I can give you the answer. Nope.
As far as I understand NSA can legally intercept packages and can legally install undetectable surveillance devices. As long as they are not using collected surveillance data, legally they are fine and they do not absolutely have to hide their activities at all costs. Hiding large scale operation is difficult and plugging every information leak is expensive. So they are not necessarily prioritizing that. So, yes, there is a change that we simply see their activity. And yes, it could be just an Amazon bug.