"what is with the silent treatment? "
I'd suspect their SOPs and ROEs may require them to maintain radio silence at times, including the times they are sallying out or returning to port, and may be most vulnerable to attack.
OTOH if you are about to violate a security zone, they are (contrarily) required to give you a warning.
So that's what it all comes down to, rules. You can probably write to a pr
office and get specifics of what to accept, and what they are normally allowed or required to do.