Okay, this is easy to see but difficult to explain.

Look at these two pictures (left, then right):



When you walk on the first picture from left to right you hear the footsteps differently on the road. Dirt-Road-Dirt. This is okay.

Now fell the tree so that it does not touch the ground where the road is. When you run over the tree you should hear Wood-Wood-Wood.

Instead you hear "Road" where I made the red signs. As if the tree was plastered with cobble stones

I consider this a bug because IRL this is not the case.