The example you pointed out at 3:15 is one of the most disrespectful things I've seen done to someone in the ring lol.
With that said, I love how he feints as well but like someone pointed out, it's not for everyone. Rigo has incredible defensive reflexes. He can get away with this stuff.
The other reason why he does it is as a way to build torque for the shot he is REALLY looking to throw. Sticking that straight left out there was almost like him winding his body up to test that right hook and he timed it JUST at the moment when his opponent jumped in thinking he was vulnerable (wrong).
Slick stuff like that makes me wet my pants and I definitely incorporate similar stuff into my game.