A proposal may have a validity period or assumptions about product availability. If those conditions change, the revised scope should identify the effect. Substituting materials is not merely an administrative change when compatibility or appearance differs.
What to do next
Ask how pricing changes and unavailable products will be communicated. Require the revised product identification before approval. Keep the original and accepted revisions together so the final project can be checked against what was actually authorized.
Related Perkins guidance
Contact Perkins Roofing to discuss your roof and the appropriate next step.