Yeeaaah... but I still wouldn't do that with a loose grip like that guy has... if that thing kicks, it's not gonna be held well enough to control the saw... Efficient? Yes. Good for a guy that cuts timber every day? Yes. Low risk? No... if one were to slip up/have a brain fart while using techniques like this, serious injury and/or death can easily occur... not to mention how much easier it would be to accidentally brush the kickback zone of the bar against a branch or something... and if there isn't another branch or something to catch it, you may be the one that's gonna catch it...
There's my criticism...
In practice, the saw is held as firmly you normally would. Well, unless you have a death grip on yours. You wear PPE to protect against most kick back issues. It is low risk when done right.
And it has been practiced for years by professionals in Europe with little incident. Professionals make something that could be potentially dangerous look fast and easy. If you are uncomfortable trying such techniques, I suggest you don't.
You can kill yourself slipping in your kitchen making salsa... if you are afraid of saws, stay out of the kitchen.