The article is written like this is a silver bullet with hand waving pseudoscience justification which implies it is total bull.
What I saw in this video was like looking back 30 years and it made me happy. You're underestimating our kids to think we can't let them loose for a good game of bullrush and they are more aware that they are being watched than actually just playing the rules of the game. Also remember that Rugby is New Zealand's national sport and these kids grow up watching it and knowing the rules. I'd bet some of those kids end up in the All Blacks.
That being said, I also think rugby is a silly game.
Yes, watching the video reminded me that no-one taught me how to tackle when I was playing Rugby as a skinny 11 year old. Good to see the kids at the school have someone to help them avoid those common injuries and still get some decent play in.
Thing one thing I would say is that it was a different time and I think we have became more fearful of the potential dangers out there. We are presented with extreme events and begin to think that this is the way of the world. Parents (rightfully) become fearful for their children. But, for a lot of us, we are lucky and live in a very safe environments, and in such environments children should be aloud to explore, imagine, and enjoy their childhoods.
Bullying grew more and more, i suspect because we were doing less at playtime and spending more time hassling each other.
I got into far too many fights towards the end of primary school than my first couple of years.