It’s only invalid if it generated errors.

I understand this line of thinking, but unless they specify what "flavor" of JSON they accept, I think it's safe to assume they only accept what's in spec. What I find weird is that they immediately contradict the spec with their example by writing JavaScript. Should the content-type then be application/javascript? They can easily document the parameters outside the request body instead of adding comments.

Also, yes, I know I'm being pedantic, but if I'm applying for a job, it's a two way application. They need to give me reason to trust that they're worth working for. Making up rules along the way when referencing a commonly known spec doesn't give me much confidence.

That looks like a JavaScript object. It's not incorrect sytax for a JavaScript object.