At this time, when the auto bank rec box is unchecked, all of the training rules you entered will be removed. I believe the training rules should stay even after removing the auto bank rec because without the box checked, there will be no automatic matching being done and incase they turn it back on, they do not lose the trained transactions.
Also in this specific instance, there is a bug that is unchecking the boxes for users and creates issues where they lose all their trained transactions.