From the judge perspective, I've had a number of "Imperial Porters" which didn't rate very Imperial. Just because the numbers say it's Imperial, it needs to be way over the top to be judged well. Being a little over the top won't hurt it in 23 if it's not stated to be imperial. So if the vanilla is balanced enough to seem like an oak or bourbon contribution, I'd leave it off the form, too. A typical strategy on judging 23 is to tick through all the words on ingredient list and description and ask if it's there. If it's borderline enough to be attributed to something else, it's better to make it seem like that "something else" is just that much cooler.
Last weekend, the BoS judges were confused at the announcement of the top prize. It was a 13B Sweet Stout, but the beer name was Hazelnut Stout. Turns out they used so little extract that it only contributed a nuttiness to complement the malt bill. Had it been in 23, it would have flunked out.