Well when you and your phone or car move then yes in almost real time the GPS knows where you are.
Now imagine you are 1000’ long and your GPS is located at one end. Now spin around on that axis. The GPS does not move but your other end is now moving in a 2000’ circle.
Rotterdam Express is a medium sized container ship and was anchored about 500 meters from the site of the alleged pipeline break. IMO, it would be a stretch to have a ship properly moored rotating around its placement in relatively calm waters.
In any event, the ship was bordered near SF by the CG. IMO, it does not look like the monitoring authorities believe this ship was the culprit as the distance from the spill was 500 meters. According to owners it had not moved during the time of the spillage. This ship happened to be the closest one to the break and as such was investigated.