All I know is that the system simply won't let you check out a BMW without manager authorization even though it allows you to make the reservation and all. At SAN and LAX they probably just let you do it. This employee wanted to follow the rules that's all. Also the XTS is not technically a signature car anymore. It's a luxury class car now, though a lot are still tagged as signature.

Edit: It is still a "cool car." So if she wouldn't let you have a Mustang she shouldn't have let you have a XTS. I don't really know what she did.