It is not CGI. Also here is google-translation of the current top-comment:
Quote: "And why the real helicopters don't fly like that?"
...
Quote: "Pressures on the base of the blades so much more. When the required strength and stiffness of the blade in a predetermined fixed position can not make a quick responsiveness to their management. This helicopter blades on the opposite slope of the change in a split second. If so turn a real blade, it curl. For similar reasons, for example, only small flying insects quickly, and large birds do not fly like insects. In this small bird, hummingbirds fly like insects."
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