When modelling in SEGW there is no chance of having same Navigation Property for the whole project. Service builder will not allow duplicate properties to be defined inside a project.
Even if same Navigation Property is defined in other project its still fine because that would be specific to Project created in SEGW.
However did you check the filled inside IT_NAVIGATION_PATH when you fired the below URL's
/ProductCollection('AD-1000')/ToSupplier
/SupplierCollection(10000)