Turns out, we hit something as new as last week:

GitHub

Strict mode for JSON parsing · Issue #2295 · google/gson

As noted in the documentation for JsonReader.setLenient, there are a number of areas where Gson accepts JSON inputs that are not strictly conforman...

JSON lib devs are struggling to figure out a standard to escape or not escape \u2028 and \u2029 #[4] we need to clarify how to escape the String of content in NIP-01 before the string is converted to bytes using UTF-8 and then hashed. Which characters get escaped and which ones don't