I don't think this was actually one complete flip. The shot is edited such that it is likely someone doing a flip on the scooter into a bed of foam blocks / lake / whatever - often used to practice BMX stunts. He's completing the loop on an angle.
Then there is a shot of him 'landing' which actually starts with him only a few inches off the ground and not falling at a fast rate or the correct angle. He's 'landing' straight. Likely he did a small jump over the crest of the landing ramp from the reverse side, catching only about 10 inches of air and landing on the rear wheel.
Not to say this is impossible, but the editing of the shot is suspect and suggests there wasn't a single complete loop performed.
I still remember when the first backflips were being done on BMX bikes 20 years ago - we thought that was incredible at the time