Deer don't stop feeding, and they don't stop moving. The "lull" is really the result of the larger family groups and bachelor groups breaking up and going their own way and a change in food sources. This gives the appearance of less deer movement because when you used to see a group of 5 bucks every day at x time, you will now see 1 buck, maybe another, etc. and they are searching and preparing for the rut to come.
The change occurs as their summer food sources change - farmers cut their corn, harvest their crops, etc. Green fields are browning and losing nutritional value. They simply change their patterns this time of year. In the coming weeks, the bucks will become singularly focused and will become more visible obviously.
I do agree that whatever you were hunting in September (food, travel, etc.) likely is no longer producing as well. That's not because the deer quit eating and moving, or disappeared, they simply changed their pattern, as should we.