They could have addressed the issue and it doesn't matter if it was the warranty or some other mechanism. eg all they had to say was that if bluetooth failed on that model then they would replace the phone or give you a certain amount of credit towards a new one.

Bluetooth is critical functionality for anyone who commutes by car, and those who talk a lot. It isn't some rarely used side feature. A phone where this stops working is very notable, a huge pain and you are forced to resolve it almost immediately.