I obviously wasn't on either vessel, so I'm not going to try to second guess anybody, but it seems to me that another possibility might be that he initiated a course alteration to steer clear of you. It takes those big guys awhile to actually change course though, so that meanwhile you altered course back toward his new course. In other words, from his perspective, he might have changed course to keep a safe distance, then you turned back into him. You might be right, he could have been screwing with you. Some time ago, I watched what turned out to be a high speed ferry in dense fog on my radar near Catalina Island that I'm convinced was to trying to scare the hell out of a couple of small boats (multiple course changes resulting in very close encounters with multiple small boats). In your case though, with a single course change on his part, it just seems likely to me that he was a little late in noticing you (do you have a send & receive AIS or one that just receives?) and altering course.

Doing the Baja Bash one night a few years ago, I altered course 45 degrees to port to avoid a radar target ahead only to have him turn back onto a collision course. I then altered course another 45 degrees to port only to have a closest point of approach that was still too close for my comfort, so I then turned another 180 degrees port to get away from him (for those of you that are counting, I've now made a 270 degree turn). Once I was well clear of him, I then turned a final 90 degrees to port, completing my 360 degree turn and resumed my original course. Rather than assuming the other guy was screwing with me, I prefer to assume that he was a fisherman and was either completely unaware of me and just tending his lines or net or that he was aware of me and was trying to keep me out of his lines/net. I know I've had the latter happen to me before as that time it was a panga that eventually came up alongside of me and asked me to follow him around his net.