A manufacturer is under no legal obligation to provide a crate motor if the can repair the existing one to satisfy a warranty claim. From a post above, someone is speculating that Hyundai actually would prefer to use a crate motor if they had enough to go around, but my have used them all up (and they are not manufactured any more).
When doing it through BBB routes you have more control over what/how your car is fixed. HMA isn't going to just give you a replacement that easy...its a fight and if your going to fight, fight!