The slabs could have a very different grain than a live tree that was sawed. They call it Spalted, I think it's a fungus and since the tree was on the ground and decaying it's possible.
Sometimes the grain lines are also blacker in a cherry than a live tree if the tree was dying or dead in the air at the time of sawing. Some reason cherry does that. It's a unique look also but it isn't spalted, imo.
Personally I don't like the look of neither in cherry but I won't turn down free wood or a chance to salvage that log before it's gone to rough.