I'm not arguing if its right or wrong, but the author sure doesnt seem like they understand what theyre talking about.
I think they understand - to a point. It's just a few steps removed from what they normally think of, so is easily confused as "from thin air".
If they solicited people to draw doodles and simple cartoons in their free time and send them in, and they would auction those off, it wouldn't be "from thin air".
If you have your computer randomly generate fractals or images and send them in and people purchase the aesthetically pleasing ones, that's also not "from thin air". You've just traded your direct effort for use of your computer, which includes increased energy costs, and possibly slowed computer usage.
Replace images that are aesthetically pleasing for a bit of cryptographic hashing that helps the whole market, and you're where we're at today. Costs are there, they are just so small as to be easily lost in the rest of your costs, and the work is there, just abstract and automatic enough that it's easy to not realize it's work. Fundamentally it's no difference than everybody contributing a doodle though.
I'm not really a proponent of cryptocurrency one way or the other, but I'm not sure it's any less absurd than generating money out of paper/textiles and ink. Drawing a picture of a $1 bill on an appropriately sized piece of material doesn't make it money, the supply, demand and efficiency of exchange does (and the demand is often generated by a backing from a government, but doesn't have to be). We had private bank notes long before we had government backed notes.