"Unrepairable" phone

No. Apple did not say that it was unrepairable. They said that they would not repair it. That is not the same as "unrepairable." They offered you an out of warranty replacement for about half price. Apple does not have the facilities in Apple stores to do other than very minor repairs on phones, and they don't have technicians in stores capable of doing other than minor repairs. Instead they replace the phone and send it to a central repair facility where it is refurbished by skilled technicians with sophisticated equipment.

Independent repairers can sometimes fix iPhones for less than Apple would charge for a replacement. You are free to use their services, but Apple takes no responsibility for their work. Just like your auto manufacturer takes no responsibility if you take your car to an independent auto repair, but you are free to do so.

We weren't there but in my observation they always mention an out-of-warranty replacement. If they didn't go back and talk to the service manager.