The problem is insufficiently analysed by the article author and the commenters in this thread so far. It is very superficial. The recent thread "Can’t use iCloud with “true” as the last name" https://news.ycombinator.com/item?id=26364993 went deeper. Let me take up its relevant particulars into this thread. The article author hitchdev does not say it outright, but it is heavily implied that the YAML file was edited…
The article author also misidentifies the version of the YAML spec (calling it 2.0, which doesn’t exist; the behavior is from YAML 1.1, and this class of problems motivated a bunch of changes in YAML 1.2, which has been out since 2009.)
But the article author isn’t trying to analyze the problem, he’s trying to rationalize why what is notionally a YAML-processing library just ignores the spec.