It sounds like this independent licensee may be purchasing used cars, hence the very high miles from a relatively new facility. It's possible these formerly belonged to another rental agency that is also known for keeping its cars until they have a lot of miles (cough, cough, Hertz).

By franchising, Sixt not only lost control of its standards, but also missed a one-way opportunity with its corporate stores in ATL. My understanding is that there is some natural traffic between western NC and ATL.