It all depends on the definition of your project, where you have a box to decide which kind of project stock you use:
- no stock
- valuated stock
- non valuated stock
see the Step by step configuration for Valuated Project stock - ERP Operations - SCN Wiki
If your material type is quantity only (equal setup to UNBW) then it is standard that an account assignment is mandatory and despite of this account assignment it always creates stock, hence you get a storage location.