Work order operation sequence "1" with direct material charges applied

I have a work order operation 1 that has costs applied from a non-catalog purchase.  I'm not able to reference an operation 1 for material requirements from within a work order, but I can charge to an operation 1 if I go through iProcurement.  Reviewing the work order, the purchase costs are included in work order costs, are applied to the correct department, and are applied to operation 1, all as expected.  I don't see the harm.  Is there anything that I might be missing?