They may well be sabre rattling and holding exercises. That would not surprise me in the least. This hiding in shipping containers on cargo ships nonsense is laughable.
It's not. Chinese converting shipping containers to hide weapons/troops has been open knowledge for some time now. I heard about it years ago but have seen articles quite recently. Here is an example, and it's not from the lady who did the translation. It's from the Naval War College:
https://digital-commons.usnwc.edu/ils/vol97/iss1/45/