Electricity likes the path of least resistance to ground. If you are only touching with one hand, most likely the current well run down that side of your body to ground more or less. If both hands are touching it makes it more likely for the current to cross your heart which greatly increases the risk of death
This is why in electrical trade you're taught to use your right hand, with your right foot below your shoulder, and left leg out (when doing anything sketchy).
If you do get shocked then the current will travel down the right-side of your body, and out through your right leg.
That's not to say throw caution to the wind, but some people need to do risky things (that's why sparkies get paid a lot).
For example, a guy I used to work with had to repair a switchboard at the hospital, which supplied power to the theatre rooms. Time sensitive matter as I'm sure you can imagine.
This guy was a pro, and was wise to take the safety precaution. When it came time to power back on the switchboard, not only did he right-hand/right-foot, he shielded his body and face with the switchboards door panel.
Something inside blew up, and he got his hand burned quite badly. Fortunate for him to be at a hospital. In this case he didn't need the right-hand/right-foot technique, but if things happened differently, it could have saved his life.
It obviously isn't. You can see it sparking in the video as it energized the wire. If it was to ground those minor sparks would have been massive arcing and that wire would melt.
You're not wrong lmfao. But it's exactly like "I don't need a helmet, I simply won't get hit".
Im not convinced with this much juice it would have made a difference, and if you're committed to doing it this way you ARE probably better off doing whatever helps you avoid the worst, not mitigating it, BUT there are a LOT of stories of people who have been saved by best practices.
Every line of Osha (or whatever it is in your country) is written in blood.
Grabbing with both hands you make it extremely easy for electricity to go through your heart. Electricians are usually thought not to use both hands for anything if possible, since if cable is powered chances of serious injury are slimmer. Also twist at the end was to increase tension on the wire.