The equipment would have to meet IMO performance standards. They are very detailed.
I’ve never seen the AIS display dependent on course. The only thing that comes to mind is dangerous targets. That’s a feature that changes the color of the target icon from green to red if it’s under a set CPA TCPA parameters. Those targets would change with course.
This might be a problem with the article;
Captain Mike Jessner, a Captain for American President Lines, is working to shed light on this issue and to solicit international support in order to change the status quo and outlaw the use of vessel units on fishing nets. Captain Jessner has seen first-hand how these AIS buoys overload the ship’s equipment. On a recent transit between Shanghai, China and Busan, Korea, Captain Jessner photographed the ship’s ECDIS with hundreds of targets on the screen from broad on the port bow to broad on the starboard bow. It appeared that traffic was clear off the starboard beam and out further on the starboard bow; however, when he changed course, hundreds of AIS targets appeared on his new course line. The equipment identifies these as vessels and it is only able to track a couple of hundred at a time. When there are hundreds in use on fishing nets, the ECDIS cannot distinguish which are vessels and which are nets, so they all appear as vessels. As the ship changes course**, the ECDIS drops the targets that it no longer sees as dangerous** allowing for acquisition of other targets on the new track, which are not visible before the change of course.
AFAIK ECDIS displays everything, the user can set what is dangerous.
If the ECDIS is in fact capable of screening AIS targets the AIS on the radar should be all the targets. In heavy traffic the radar is more useful then ECIDS.