The author actually address this a bit in the 2nd and 3rd paragraph. The US has added a layer of complexity on top of the plain vanilla mortgage. For the rest of world, mortgages are a way to pay for the house over time. However, in the US, they are into derivatives of the house price (pool them together, sell off the risk (rate of change of house price)), hence the title of the article: Mortgages are a manufactured product.

Edit: now that I think about it. The first level is just buying house with cash immediately. The mortgage is the next level of complexity, adding time dimension. The article is about the 3rd level complexity above that (securitization of the 2nd level)! Turtles all the way down.