No, they would replace the bumper.
I guess that depends on the laws in your state - and how much of a fight you're willing to take up with the dealership / company producing said defective car/product.
That said, you'd be amazed at what you can get replaced given the effort you put forth.... It really depends on what you find acceptable and normal - and from this thread - people apparently don't take the appropriate stance with a defective product nowadays.
Considering that this nation was built upon the notion that it's expected that a company stand behind it's product and provide a "new" replacement in the event that product fails - it's certainly sad to see that many people now take the easy way out because they just don't want to be bothered with the alternative.
Whether it's $.02 or $20,000 - I expect a product to work as advertised and be free from defects. I also expect that product to be replaced, without question, with a new product in the event that that product fails within the stated warranty period. That's my personal expectation - and to date, I've yet to have any company deny a new replacement when I've asked for it - when giving the company valid reasons as to why I'm requesting a new product replacement.
YMMV.... I guess it really depends on how persistent you are in what you request.