This is good advice in general, but Rails used the wrong kind of parser for this kind of data. JSON is not YAML. A YAML parser does not provide the same guarant

This is good advice in general, but Rails used the wrong kind of parser for this kind of data. JSON is not YAML. A YAML parser does not provide the same guarantees as a JSON parser about its output. It doesn't matter if both parsers are completely correct if you use them inappropriately.