Hell, the kid had fun with it. If you have the tools and the parts and the time have at it. That's not the silliest or least safe motorcycle to ever come down the pike although it has a proud place in that tradition.
Anything you build with your own two hands that gives you satisfaction or teaches you is worth the blood, sweat and tears... mostly.
That fella saw the possibility and he ran with it. He went as far as to make a "SEE, IT WORKS" video. I think his concern was that his critics claimed it didn't work at all, not that it didn't work worth a tinkers damn.
There's a saying that I have butchered to the point that I can't remember the original quote. Something about Experts are just folks that have taken a notion and screwed it up in every way possible until they are left with the right way.
That boy has skills and now he has knowledge that explains to him why those that came before him opted not to employ that particular linked leaf spring tech to motorcycle design.
It would make a good steam punk prop if it had some brass sprockets and wire trinkets.
If that engineering exercise offers too much front end for you here's the other end of the spectrum
I have to respect the old school engineering that went into this build. Is it practical; no. It is a great profiling and show bike though and my guess is that is exactly what this young builder had in mind. I give him a "well done" and two thumbs up.