"Things that are different are not the same" goes for the Gentiles to whom Paul was first sent and those to whom he was later sent. Yes, those to whom Paul was first sent became members of the one Body with the Gentiles to whom he was later sent, but some Gentiles (called Greeks in a KJB) got to hear the gospel of Christ preached to them because they were found in the synagogue of the Jews fearing God (Acts 13:16 KJV, Acts 13:26 KJV) and seeking a blessing according to the promise of Genesis 12:3 KJV (Galatians 3:29 KJV). No, they did not know that their blessing would come in the form of a mystery/the preaching of the forgiveness of sins (Acts 13:38-39 KJV)/ that Christ died for their sins, was buried and rose again the third day for their justification(Romans 4:25 KJV, 1 Corinthians 2:6-8 KJV, Romans 16:25-27 KJV. 1 Corinthians 15:1-4 KJV).
We can try all day long, but we cannot say the same thing about the Ephesian Gentiles to whom Paul wrote the letter. The "you Gentiles" that Paul became a prisoner of Jesus Christ for (Ephesians 3:1 KJV) in time past were without Christ, being aliens from the commonwealth of Israel, and strangers from the covenants of promise, having no hope, and without God in the world. These Gentiles were not found fearing God and seeking a blessing through Israel! They were worshiping the goddess Diana as late as Acts 19 (Acts 19:28 KJV)!
Ephesians 2:11 Wherefore remember, that ye being in time past Gentiles in the flesh, who are called Uncircumcision by that which is called the Circumcision in the flesh made by hands;Ephesians 2:12 That at that time ye were without Christ, being aliens from the commonwealth of Israel, and strangers from the covenants of promise, having no hope, and without God in the world:
We, by extension are just like these Gentiles (like the Ephesians to whom Paul wrote the letter) as we didn't have anything to do with Israel! There was no Israel by the time we came around!
This is where we fit in to God's mystery plan, beloved! It was unsearchable/hid in God that we should be fellowheirs with them and of the same Body beginning with Paul (on the same ship/the fellowship of the mystery) and partakers of God's promise in Christ BY THE GOSPEL (1 Corinthians 15:1-4 KJV) until the dispensation of the grace of God was given by God to Paul to usward!
Ephesians 3:1 For this cause I Paul, the prisoner of Jesus Christ for you Gentiles,
Ephesians 3:2 If ye have heard of the dispensation of the grace of God which is given me to you-ward:
Ephesians 3:3 How that by revelation he made known unto me the mystery; (as I wrote afore in few words,
Ephesians 3:4 Whereby, when ye read, ye may understand my knowledge in the mystery of Christ)
Ephesians 3:5 Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit;
Ephesians 3:6 That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel:
Ephesians 3:7 Whereof I was made a minister, according to the gift of the grace of God given unto me by the effectual working of his power.
Ephesians 3:8 Unto me, who am less than the least of all saints, is this grace given, that I should preach among the Gentiles the unsearchable riches of Christ;
Ephesians 3:9 And to make all men see what is the fellowship of the mystery, which from the beginning of the world hath been hid in God, who created all things by Jesus Christ: