I have seen wood in cement foundations before that was added as a siding nailer. That could be what you have here. If so, it shouldn’t be touching the dirt. But are you sure that’s wood? In the first picture it looks like cement to me. I’ve seen the wooden forms leave an indention in the cement that gave it a “grain” appearance.
It looks like there are screw heads visible.
Wood against the dirt is bad news, will decay. Hard to tell if it’s pressure treated variety.
Did the owner offer any insight ?
What part of the country are you in?
the grey is the wood weathered and yep nail heads. definately embeded wood not indentions from forms this is taken in laporte indiana .