You are speaking about basic intricacies (the physical and spiritual differences\spiritualizing what should and should not be spiritualized) here and "The fact that Jews deny Christ means they are not of Israel.", doesn't separate them from being of the same "physical" lineage or ancestry.
"they are not of Israel", is being taken too literal, it could somewhat read as, "the spiritual Israel", but I didn't write the book (the verses are written this way deliberately, by the way). This points out their spiritual disobedience and not they they are completely separate from others of the same physical lineage\ancestry.
There are verses similar to what you wrote: "The fact that Jews deny Christ means they are not of Israel.", not gonna be looking them up and there are others in the same category, such as, "you are of your father the devil" and "are of the synagogue of Satan", but these don't separate them from their physical lineage\ancestry.
"I can understand the differences between the spiritual and the physical realms. And, it is a good required study pertaining to spiritual matters."
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