After the cost engine expands process templates, it considers each resulting routing in turn. For each routing, it evaluates the routing’s stock selector, and then for each resulting stock, it visits each process in the routing in order to perform process feasibility checks, machine selection, operation assignment, and operation and process costing (see Cost Engine Details).

So each stock selector is evaluated in the context of a particular process routing. But, for that routing, machines have not yet been selected, operations have not been assigned, and no processes or operations have been costed.