In the context of the other landings in that 10 minute clip, it was one of the least 'stable' but it's unfair to judge the pilot's competency when you have no access to the instantaneous wind readouts.
Some of the approaches, even from the medium jets, were uncannily smooth; still others looked fairly stable but still led to go-arounds. I'd say the conditions were fairly variable.
The 777 wing drop in the flare was significant and I'd guess was related to a gust. The pilot's instant and probably instinctive reaction was successful in levelling the wings and once complete the aircraft was pretty much on the ground. Not much point in performing a go-around at that point, unless you fancy going through the whole process again?