"If some of the branches have been broken off, and you, though a wild olive shoot, have been grafted in among the others and now share in the nourishing sap from the olive root, do not boast over those branches. If you do, consider this: You do not support the root, but the root supports you. You will say then, "Branches were broken off so that I could be grafted in." Granted. But they were broken off because of unbelief, and you stand by faith. Do not be arrogant, but be afraid. For if God did not spare the natural branches, he will not spare you either." Romans 11:17ff [emphasis mind]
And this one:
"I do not want you to be ignorant of this mystery, brothers, so tht ou may not be conceited; Israel has experienced a hardening inn part until the full number of he Gentiles has come in." Ro. 11:25
How do you reconcile these verses with the article? Dispensationalism aside, Paul is making a very clear distinction between the church and the ETHNIC jewish people in these verses.
I think you have a valid point and I believe the author would agree. A distinction should be made. God's plan of salvation only included one plan-justification by grace through faith. Gentiles, by God's grace and mercy were grafted into this system-not the other way around.
However, they did not separate them from the church as the dispensationalists do. The ethnic Jews would join the true, spiritual Israel (the continuing Israel of God), the body of Christ, the church. See Eph. 2:11ff. Dispensationalists speak of the Jews as separate froom the church while Paul and the rest of the NT speak clearly of the the unity of the people of God (Eph. 3 calls it the mystery, once kept hidden for ages, now revealed).
I suggest you see John Murray's commentary on this passage on Romans to which you refer. Even if you disagree, you'll get the answer to your question.