I would think it is real. It is producing a noise exactly the same way a clarinet does, by vibrating a reed. A thick leaf should do the same thing. Get yourself a normal piece of paper and you can make very similar noises if you do it just like he is doing it. Hold onto the paper with your index finger and thumb real tight and hold to your mouth and blow. You will get sounds if you experiment a bit.
Yes, I agree it's real. Although at frame 1.27 he takes the leaf away from his lips - and the sound continues. So he may have been leaf syncing.
Actually, he is using two leaves or one folded. The air vibrates the two leaves together forming the sound - as TomS describes in all woodwind instruments. He changes pitch by loosening or tightening the leaves with thumb and forefinger.
When I was growing up, we made music with a wide blade of grass (about 1/4 inch or so). I would place my thumbs side by side, holding the blade of grass between them. Notice if you do this space between the two joints widens. This aperture w/the grass held tightly between formed the grass reed. Vibration of the grass reed produced the sound. If you bend the thumbs at the first joint, the aperture formed widens - and changes the pitch.
We then formed a pocket with the rest of the hands clasped or cupped together. We made changes in tone by opening and closing the hands.