The YAML 1.0 spec says no such thing, it doesn't even mention JSON. Neither does the YAML 1.1 spec. The YAML 1.2.0 and 1.2.1 specs do say exactly that. 1.2.2 no longer does, but it reiterates that the primary focus of YAML 1.2 was to make it a strict superset of JSON.

You're right. I must have clicked the wrong link, the YAML 1.0 spec doesn't mention JSON. The quote was from 1.2, thanks for pointing that out!

However this wasn't really true till 1.2 if I am reading the spec correctly. Plus many parsers default to 1.1. =\