I have a few different takes on this incident.
First, as someone who works on a container terminal, in a harbour with a narrow channel from the entrance to the end. My understanding in our harbour is that a clear zone of two nautical miles is required both in front of, and behind oil
and gas tankers. Also, rules set out by our regional council prohibit any movement of tankers, anywhere in the harbour, between sunset and sunrise.
Harbour control which is situated at our container terminal, which is about half way up the harbour, controls all vessels over (I think) 50 or 70 feet in length. They are required to gain permission to enter the harbour from harbour control via VHF.
I have heard of an incident when harbour control informed the pilot of an oil
tanker that there was a recreational boat within the allowed distance and asked if that was acceptable. The pilot apparently replied that there wasn't anything that could be done about it at that point, but he was not happy about the situation. I was of the impression that the pilot felt under increased pressure, while being responsible for a ship carrying a large cargo of U.N. classified dangerous goods, which brings me to my next perspective on this incident.
What is known in the U.S.A. as HAZMAT is more correctly called dangerous goods. After the second world war a system for moving surplus explosives around europe
was developed with the United Nations. Several classes
of dangerous goods were developed over the years (nine at present) with explosives coming under class 1. Class 2 covers gases and class 3 covers flammable liquids. Class 4 is flammable solids etc. with other classes
covering radioactive's,corrosives, infectious substances, etc.
These UNDG's have international regulations
for labeling, packaging, transportation and segregation, so that they can be carried across international borders in a consistent manner. When I was a truck driver, I was licenced to carry DG's (still are) and we carried emergency
which list all of the (several thousand) individual U.N. numbers for specific DG's which cross referenced with sections on emergency
responses for, you guessed it, emergencies. A person responsible for a vehicle carrying DG's is held very accountable for compliance of the relevant regulations
in carrying a specific cargo and it's segregation from other specific cargoes and passengers. In the case of a ships master (presumably partly because of the high volumes) the bar of accountability is extremely high and their testing for competency is also much higher than for those operating land based vehicles. So they would expectedly be very concerned about other boats in proximity, particularly if they are navigating a narrow channel.
My last perspective is that of a boat owner in a harbour, in which I am, for the most part, restricted to using the channel. I have a VHF on my boat, though do not have a licence to broadcast with it, I can listen to it though. My practice is to keep an eye on the shipping
forecasts and listening to harbour control on the VHF, because I do not want to find myself stuck in the channel with a large commercial vessel, which has limited manoeuvreability.