Overdraw is overdraw - its literally caused similarly or exactly the same way.
Which is
By having many transparencis and requiring a single on screen pixel to determine if it has to color or not many times over.
Now i have no idea why your grass mesh which looks to be solid has ehat appers to be high overdraw where it shouldn’t
But if you look closely this is also visible on the green section.
So, is the material transparent or are you instructing nanite to rander with opacity?