I really don't know if it exists or not. Reason being, I rarely get to hunt enough during October to notice any kind of change in sightings. So far, my whole season has been somewhat of a lull, since about June... I've had virtually no shooter bucks on any cameras this season and I'm really starting to wonder. Are the bucks still bachelored up and feeding somewhere else? Is a neighbor throwing down corn and apples by the truckload? I don't have a clue.
A couple days ago I walked a property with a buddy of mine, and we found a shitload of deer sign. Fresh rubs and scrapes were littered up and down every fencerow. We saw a couple small bucks running together, still feeding in the dried out beans. Based on what I saw, the activity has not slowed down as of late. Now whether those rubs and scrapes are being made during daylight or not, I don't know.
My personal opinion on the October Lull, if there is such a thing, is that it's just a matter of a hunter not adapting well enough to the changing behaviors of the whitetail. The deer don't just stop moving for weeks on end... If you're not seeing them, you're not in the right spot at the right times.