A repair can sometimes be confined to a defined area, but the boundary must work with the existing roof assembly and applicable requirements. Convenience alone is not a sound reason to stop a repair at an arbitrary line.
What to do next
Ask how the contractor chose the repair boundary and will integrate new materials with retained ones. Compare the condition of neighboring slopes. A written scope should explain transitions, excluded areas, and what discoveries could change the proposed extent.
Related Perkins guidance
Contact Perkins Roofing to discuss your roof and the appropriate next step.