The current RFC recommends the use of an object or array for interoperability with the previous specification. JSON being a bit of a clusterf* of variants, they tried to make the RFC broad then place interoperability limitations on it. (lenient in what you accept, etc etc)

Because I just discovered that there was, at least once, a specification that actually defined JSON that way, where previously I had thought it had only been ambiguously described, and I thought that was interesting.