OK, I found it again. Page 15 of this document.

http://www.cooperindustries.com/cont...-2017-sccr.pdf

So it's not exactly as I had said, but the issue remains. It's not in 409, it's a new requirement in 670.5(2) requiring MACHINERY to be field labeled with the SCCR information. So if your "machine" has two panels on it, one marked at 5kA, the entire machine must be marked as requiring 5kA or less before it can be hooked up.