I was equally surprised by the article, I think the inventor deserves a lot of credit for this. According to how the article reads magnetic particles interact with the magnetic component of an electromagentic wave and absorb it. I simply extended this product's concept to the idea of radar stealth, which of course would need considerable research and refinement.
Radar bounces off metal just fine, that's why ships for example show up on radar and how radar dishes work. Of course that's also how aerials work and they absorb electromagnetic radiation.
Presumably unmagnetised particles would reflect radio waves if they were less than the wavelength of the radar wave apart. The innovation here is that they absorb the waves if magnetised.
I don't blame R.L. for not knowing about it, this is either an obscure effect or something the inventor found for himself.
I wouldn't be surprised if this is actively being researched now for radar stealth, throw a lot of money into it and who knows how it might turn out.
Creating an aerial system to cover something like a plane to absorb all radar has been actively researched for many years.