I think everything in that post is correct. I think you don’t understand what it is saying. In pretty strong terms, the excerpts you reproduce say, in so many words, Bellei was naturalized. He doesn’t have a constitutional right to US citizenship, at all. But here is a statute that gives him citizenshiup, and we (the court) have to decide if citizenship, once granted by statute, can be taken away by statute.
As you said, I am a crappy layer....I am not making any claim to the contrary, but I can read. And I can interpret intent and the effect of changes in law. And I do have a good idea today what was in the mind of the founders when they wrote the article.