I think that is almost certainly true. I did the same test with my new Model Y last night, and found that it seemed to track a little too far to the RIGHT. But after observing it carefully, I realized that it was in fact centered in the lane, and that my own driving had a tendency to hug the left side of the lane.
My biggest concern about Tesla Vision (based on very little experience so far) is the auto-brights. I turned them on several times while driving after dusk last night and found that they frequently went on while oncoming cars were less than 100 yards from me, and also when tail lights in front of me were at a similar distance. If I were in one of those cars and found someone else's brights shining at me, I would be cussing that driver out. It's a serious problem, and Tesla needs to get it fixed. For now, I consider autopilot to be usable only in the daytime because of this flaw.
It shouldn't be hard to get this right. My Mazda does it perfectly. It turns off the brights instantly when there are either headlights or taillights ahead of me within a quarter of a mile or so.