There is such a thing as meaningless concepts or concepts that do not point to some sort of thing (i.e. phenomenon.) “Perfect circle” might be a meaningful concept provided that you assign to it some kind of meaning (i.e. if you make it point to some sort of thing) but in the case of James, and also S57, it is a statement without any meaning. Basically, it’s just a sequence of words. That’s all it is. Words must refer to something concrete otherwise they are meaningless.
Another thing, which isn’t much relevant, is that people have evolved a common manner in which they determine which shapes are circles and which are not. Definitions are supposed to REFLECT this process and to reflect it with as much precision as it is necessary. The popular definition isn’t bad. It’s pretty good. But it becomes problematic when people take it literally.
They don’t start with what is real. There are circles EVERYWHERE around us. But because they take words literally, they won’t acknowledge this. They don’t understand that when you take the popular definition literally that you strip it of all meaning. There is no way in hell that you can identify a shape that has an infinite number of points on its boundary that are equidistant from the center of that shape.