Likely the plastic protective undertray was crushed/torn away at some point. I wouldn't let that deter you from purchasing the fantastic machine known as the Z4M!
What's interesting is that the picture you've shown above is taken directly from a DIY from Pelican Parts (or at the very least from the same car). Any idea what that's all about?
https://www.pelicanparts.com/techart..._Replacing.htm