You are right, in Back office will be displayed all items, even though you filter by store. There is an explanation why in the back office the filter by store works in this way; if the filter by store would determine display of item or not, then there would be a case where the user would never see some goods on this list (for example, ingredients of a composite product which are not available in any store).
The items marked with "available for sale" on specific store are displayed separately on app but not in Back office. The filter by store in Back office helps to see the stock of items in the selected store.
If the question is how to get informations about what products are in a particular store, then you can use Export fuction from the specified store and then, on the exported file, apply the filter in the column "Available for sale" - Y. In this way you can filter the good of your store.