Boy, all the negativity here reminds me of all the ultralight haters in the early days, pilots looking down their noses at them because they weren't "real" airplanes... while the ultralighters ignored the "real" pilots and went right on having fun. Peter is, in many ways, recreating that early ultralight path, from simple, cheap, barely flies, moving toward more sophisticated and capable aircraft, learning (and having a lot of fun!) along the way. Not too different from Mark Stull, who kept building "impractical" airplanes just for the fun of it.
As for his YouTube videos, he likes to share what he's done. It just one young viewer gets the idea that wow, people can actually DO such things then he's done more good in this world than a hundred guys working privately in their garages. If he's making money from it, great... video editing is a lot of work.
From an engineering standpoint, his designs are crude, even laughably so... not surprising, he's a kid. But I also see some genuinely clever thinking in some of his design details. I hope he's studying engineering, because he'll be a good one. As an engineer approaching retirement age, I would love to work with a young engineer as innovative and enthusiastic as Peter.