Your SM is correct the exclusive use parking bays belong to the lot owner.
BUT
the lot owner has to comply with your bylaws regarding use of this area and generally their is a catchall bylaw regarding the looks of the lot must be kept reasonable. Storage of items without Strata approval can cause a Notice To Comply with your bylaws be issued against the offender by the EC or SM.
Also storage of large amounts of paper would be considered a fire risk jeopardizing your Strata insurance.