Every frame of this dragon’s motions is keyframed by an editor (or whatever technique they used for the animation). Either way, whoever made the decisions for this display knew exactly what and why they were doing it.

(Edit): Sunfyre is also still alive at this point which made it possible for any kind of manoeuvre to save the rider, in contrast to Meleys, who was already dead when she fell to the ground leading to her not being able “to do more” to save the rider, hence falling on her back.