Indeed, and I apologize for my ambiguity, as you are correct. By "strict subset" what I meant was a subset that attempts to reduce options, so that legality and illegality is easier to discern. That is, where Javascript accepts apostrophe and double-quote to delimit strings, JSON only accepts double-quotes, thus, "stricter" than real Javascript.

You are of course correct that JSON turns out not to quite be a strict subset in the set theory sense of "strict subset", though obviously that's a bug in the spec rather than a deliberate design decision.