Products "belong" to a Category ... this is the immediate Category that the Product is in ...

The Categories all have categories_id ...

Products use the categories_id as their master_categories_id which says what Category "owns" the Product ...

Sale Maker uses this master_categories_id to determine what Products belong to the Categories on Sale ...

If you use "Linked Products", only 1 Category can "own" the Product ... the Category that "owns" the Product is the one used for the master_categories_id ...

If you place a Category on Sale with SaleMaker, but the Product uses a different categories_id for its master_categories_id then that Product will NOT be on Sale, based on the SaleMaker Sale ...

Only the Products using that Category as their master_categories_id will be on Sale ...