But in looking up the canons of the various ancient Councils, I find that the instance I was thinking of actually was referred to in a canon of the lesser Council of Ancyra (AD 314). I am naturally mortified, but even Homer nods. I hereby issue this clarification under the editorial and royal We, but it's my mistake.
And yes, I know the number of clergy colleagues who'd even know there was a Council of Ancyra, let alone be able to identify what a chorepiskopos was, is remotely small. But I are a serious scholar and not a slinger of roadapples and therefore have a reputation to defend. So there. Neener neener neener.