Thanks for the replies. Asking is clearly the best way to know what will be allowed. But I'm bottling stuff in general for competitions in the future, not a specific one. So unfortunately I can't just ask. But I'm generally entering smaller, local competitions where hopefully folks are not over analyzing things.
I've always thought to myself that I could recognize the shorter/larger diameter bottles used for Sierra Nevada, despite them being completely free of any markings. I suppose it's all about how much the judge wants read into the bottle itself.