IIRC the gist of the article was that playgrounds should always include risk elements because otherwise the children will use the playground against its design to find those risks (e.g. climb up on top of a structure which was designed that you play inside of it). The crucial element though was that risks should be calculatable and there should not be surprising dangerous outcomes.
I have to say looking at the playgrounds available to my kids here in Sweden, I'm pretty jealous of them, we didn't have such cool playgrounds available to us (or they were very rare). It is sometimes terrifying to watch as a parent, but look like great fun.