2007 Other Hyundai Models power steering flush

Steering problem
2007 Other Hyundai Models 6 cyl Automatic 27250 miles

I had to have my power steering reservoir replaced and it was under warranty. The service department at the dealer said I had to also have the power steering fluid flushed, could the reservoir have been replaced without doing this flush? I was required to pay for the flush and labor as they said it was maintenance.