I got the old fashioned phantom braking back, so maybe you should be pleased that yours didn't change. OTOH, it now waits until closer to exits/turnss to switch lanes, which is generally good for left turns, because 1 mile and numerous intersections early was alway stupid.
I turned on sound to try to figure out what was going on here, and I'm still not sure. Why was there a single bong before the lane change? That sounded like TACC (not FSD) being engaged, but the IC certainly appeared to indicate FSD was already running. IF FSD had just engaged as the lane was being changed, then this would be an edge case where perhaps FSD shouldn't have allowed engagement to begin with (regardless of whether and how the hardware and software could/should have been able to deal with it). However, it was pretty frustrating a few minor versions back when you couldn't turn FSD on half the time, so I'm a big fan of human responsibility over dummy lockouts in such cases. As for when she disengaged, it is certainly feasible that FSD would have slammed on the brakes just fine after that, though I certainly agree that she should have disengaged when she did if it hadn't already started to slow. That having been said, I must also say that I've done what FSD did there, and I've seen plenty of other humans do it as well (usually it's because the turning vehicle isn't signaling, but AFAIK, FSD doesn't pay attention to signals yet). As I've said plenty of times before, the biggest problem I see with Tesla's FSD is that it's trying to drive like a human. Funny that you mention changing lanes so close to an intersection. Surely you've had it change lanes in an intersection (which is even worse), haven't you? Mine does that fairly often. OTOH, I think you're giving "alert human drivers" far too much credit. Most human drivers don't know half the things they should. I've seen countless unnecessary traffic signals go up as well as countless traffic signals modified to "left turn only on green arrow" for this very reason. Maybe you meant "competent human drivers," but I'm not really sure how many of those there are.
Re student drivers, I'm sure there is at least one that is better than FSD, but I'd say the majority are not.