This is too easy, so there must be a good reason why it was explicitly
left out, right?
Don't think there is. Other than if you're actually rendering a js
update, you're probably overwhelmingly likely to want 200 OK. So
nobody probably needed a different status until now.
What is the use you have with a different status code?
Don't bet. We all make mistakes, and let's be honest -- the number of times
anyone's going to want to render an RJS template when giving a non-OK status
definitely sits in very close proximity to "never". So it wouldn't surprise
me if it got missed in the shuffle, and nobody's noticed before because it's
a very uncommon thing to want to do.
On the other hand, it may have been left off on purpose because nobody could
imagine why someone would want to send JavaScript with a non-OK status code,
but if you've got a legitimate reason for wanting to do it, I cannot see why
a patch wouldn't be accepted to allow it.