Unless that is a basic security precaution in an area where ships are sitting ducks and the local nogoodnicks can track you in real time via commercially available online programs.
If going dark (at least for AIS) is a security precaution, it would be routine in a place like the entrance to the Suez. If it’s routine, there would be rules about collision avoidance without the AIS assist.
I have no idea what the rules are, but if both the Truman and Dunham had gone dark, it’s not just one captain’s mistake. At least the Truman is big enough to win most collisions. That might have sunk the Dunham.
I have no idea about the proper procedures. Inquiring minds want to know.
In heavy marine traffic when transmitting a canal, the AIS is always on. If this was an operation to transit without AIS, it’s still a fail because the procedures were not followed to inform the shipping to change course.