Sales Receipt Requirement for Repair Servicing

I brought my iphone 12 pro yesterday to an Apple service to have the touch screen checked and repaired if necessary. I didn’t have the sales receipt with me but they were able to verify in the system that I got my phone from a mobile carrier and it is still in warranty. I was also able to do turn off the Find my iPhone and unlink the device from my Apple ID as advised by the staff. However, I was refused of repair servicing because I don’t have any receipt. Is this a mandatory requirement for repair?