1. Create multiple assortments where a particular store is assigned. Ensure each assortment has different sets of products.
2. Publish couple of assortments.
3. Edit all assortments and publish only one assortment which has this specific store and set of products assigned to it.
4. Run process assortment from retail periodic section.
5. The channel products for the above store still shows all products which are not part of the published assortment.
Ideas Administrator

Please use the Revert feature of assortments if you want products removed from the channel DB.  Once they are published, they remain in the store's assortment until reverted or removed.  Putting an assortment back to draft is not the same as reverting the assortment.  You can also remove the channel itself from the assortment, or update the expiration date.  If these standard features do not work, then please file a case through customer support.