I think it’s something like:

“The general rule is that I may access the direct embeds of my type anonymously.”

Ok I don’t think anyone disagrees with that. But there are two embedded structs, both with a URL field.

But the level of nesting isn't the same; only one of them has a direct URL field.

You would get the same result if both URL fields were nested one level deeper. Being directly nested isn't the point.