- Bad news: the documentation seems to be wrong (and has been forever?). I can not find any evidence that the ortho code recognizes, let alone uses, a radius attribute - or any similar-named attribute.
- Better news: Here is a discussion of a post-processor (that I wrote) that will round-off ortho edges. It applies one radius to the entire graph (maybe that was the problem with the planned radius attribute)
[p.s. I had not noticed the radius in the documentation. Hidden in plain sight.]